Energy... beyond oil

Energy … Beyond Oil

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Energy … Beyond Oil Fraser Armstrong and Katherine Blundell

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Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York © Oxford University Press 2007 © UKAEA (Chapter 7) The moral rights of the authors have been asserted Database right Oxford University Press (maker) First published 2007 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose the same condition on any acquirer British Library Cataloguing in Publication Data Data available Library of Congress Cataloging in Publication Data Data available Typeset by Newgen Imaging Systems (P) Ltd., Chennai, India Printed in Great Britain on acid-free paper by Biddles Ltd., King’s Lynn ISBN 978–0–19–920996–5 10 9 8 7 6 5 4 3 2 1

Contents

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Energy … beyond oil: a global perspective Fraser Armstrong, Katherine Blundell, and lan Fells The problems to be solved What are the actual needs? What are the true costs of the different energy solutions in terms of human fatalities? Energy from the Sun The nature of the solutions The way forward Arresting carbon dioxide emissions: why and how? David Vincent Introduction Principles How climate change will affect our lives Taking action Technological and policy innovation Summary and conclusions Postscript Resources and further information Some further UK focused reading and sources Geothermal energy Tony Batchelor and Robin Curtis Introduction High-temperature resources Hot dry rock or enhanced geothermal systems Medium-temperature resources

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1 2 3 5 6 7 9 9 10 22 25 28 31 32 33 34 35 35 38 39 41

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Contents

Geothermal energy as a sideline of oil and gas industries Low-temperature systems with heat pumps Potential for future growth Conclusions Acknowledgements Resources and further information Web Resources 4.

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6.

43 43 45 46 46 46 48

Wave and tidal power Dean L. Millar Introduction Wave energy resources Comparing wave energy converters—‘Wave Hub’ Tidal energy resources Tidal barrage schemes Tidal current turbines Ranking of marine renewable energy technologies Assessment of wave and tidal current resources (UK) Summary and conclusions Resources and further information

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Wind energy Bill Leithead Introduction Wind energy resource Public acceptance Technical development Concluding remarks Acknowledgement Further Reading

71

Nuclear fission Sue Ion Introduction The physics of fission Cutting carbon emissions Economics Reliability of electricity supplies Potential new reactor technology Investor considerations—regulation

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50 50 55 56 57 59 64 64 67 69

71 72 77 78 82 83 83

84 84 87 88 90 93 97

Contents vii

Investor considerations—delivery and operational performance Investor considerations—waste Investor considerations—the electricity market Public attitudes The longer term future 7.

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Fusion energy Chris Llewellyn Smith and David Ward Introduction Principles of fusion Attributes of fusion The current status of fusion research The next steps—ITER and IFMIF Fast track studies Conclusions Acknowledgement Resources and further information Photovoltaic and photoelectrochemical conversion of solar energy Michael Grätzel Introduction Principles Conversion efficiencies Cost and supplies of raw materials How PV cells are developing Summary Acknowledgements Resources and further information Biological solar energy James Barber Introduction Principles of photosynthesis Biomass The photosynthetic water splitting apparatus Artificial photosynthesis: a new technology Policies and implementation Acknowledgements Resources and further information

97 99 101 101 102 105 105 106 108 109 113 117 118 119 119 120 120 120 122 124 125 133 134 134 137 137 138 141 143 149 150 153 153

viii Contents

10. Sustainable hydrogen energy Peter P. Edwards, Vladimir L. Kuznetsov, and William I. F. David

156

Introduction Hydrogen and electricity: energy carriers Hydrogen production Hydrogen storage A sustainable energy future Conclusions Resources and further information

156 157 160 162 165 166 166

11. Fuel cells David Jollie Introduction The principles Applications of fuel cells Market developments and regulation Technological developments From today to tomorrow: changing the game Concluding remarks Resources and further information 12. Energy efficiency in the design of buildings Gerhard Dell and Christiane Egger Introduction Low-energy buildings The new directive on the energy performance of buildings The future of building and living Summary and conclusions References

169 169 170 171 172 174 176 179 179 181 181 183 192 194 194 195

13. Governing the transition to a new energy economy James Meadowcroft

197

Energy politics Sustainable energy policy Socio-technological transitions Critical policy considerations

199 200 202 205

Contents ix

Transforming energy/environmental governance References 14. Summary Robert May Index

209 211 215 221

Acknowledgments

Warm thanks are due to Dr Tony Boyce, Bursar of St John’s College, Oxford, for his support for the initial one-day workshop “Energy . . . beyond Oil”, held at St John’s College in 2005, from which this book emerged. It is also a pleasure to thank the participants of the Discussion Panel at that workshop for their stimulating and insightful comments. The Panel Members were: Brenda Boardman, Howard Dalton, John Gummer, John Hollis, Robert Mabro, Michael Scholar, Simon Weeks and David Vincent. We are grateful to Katrien Steenbrugge and Nick Jelley for helpful comments on the manuscript. Fraser A. Armstrong, Katherine M. Blundell, Oxford, July 2007.

All Author’s royalties for this book are being donated directly to Oxfam, an organisation that works with others to overcome poverty and suffering around the world.

1.

Energy … beyond oil: a global perspective Fraser Armstrong, Katherine Blundell, and Ian Fells The problems to be solved What are the actual needs? What are the true costs of the different energy solutions in terms of human fatalities? Energy from the Sun The nature of the solutions The way forward

1 2 3 5 6 7

The problems to be solved Coal and oil, which are the buried products of several hundred million years of solar energy, photosynthesis, and geological pressure, have fuelled our industries and transport systems since the Industrial Revolution, a period of only 200 years. Although opinions differ as to when the peak in oil production will occur (perhaps in 2010, perhaps in 2030), it is hard to avoid the conclusion that oil is being consumed about one million times faster than it was made and, further than this, the twenty-first century, will be the century when societies have to learn to live without gas and oil (coal will outlast oil and gas by a few hundred years). But, there is an entirely separate motivation for living without fossil fuel: obtaining energy from oil, coal, and gas will continue to put carbon dioxide (CO2 ) into the atmosphere at levels which it is widely acknowledged are elevating the average temperature on the planet. Carbon dioxide is a good heat absorber and acts like a blanket: this is because CO2 molecules resonate strongly with infrared radiation causing it to be trapped as heat instead of all being transmitted into space. Global warming is already causing the polar ice caps to melt and it is inevitable that there will be higher sea levels resulting in less land for

2 Energy … beyond oil: a global perspective

an increasing population, along with changes in climate. These changes are not easy to predict and may be difficult to reverse. Either of these two motivations, be it the depletion of oil reserves or the need to arrest global warming caused by the combustion of fossil fuels, mandates new thinking from all those with concern for the future. How will future generations view our policies and our decision making today? Unless we change course now, these people will be left in a world where energy is a scarce resource and the mobility we have taken for granted in the late twentieth and early twenty-first century will be long gone. Our generation—rightly—would be blamed for knowingly squandering the planet’s resources. We would have burnt all the fossil fuels formed in the history of the world in an orgy of combustion lasting only a few hundred years. There would be no precedent for this; hitherto, no generation would have caused future generations to look back in such reproach. The laws of thermodynamics that govern the supply and conservation of energy are well understood. Even carbon sequestration, which might stem the increase of CO2 in the atmosphere, requires energy. Saving energy, though laudable and imperative, is insufficient to solve the problems that lie ahead: oil will run out and then gas and then coal, stunting the growth of the developing world. Moreover, there is no moral high ground for the developed world to stand upon and require of the developing world that they adopt principles far greener than we have held ourselves. How can we supply energy for the inhabitants of Earth, sufficient for them to enjoy reasonable living standards, without causing serious, perhaps irreversible, damage to the environment? To achieve a 1% growth in the economy of a developing country requires a 1.5% increase in energy supply. China, whose Gross Domestic Product is growing at 7–10% per year, commissions a new power station every week!

What are the actual needs? The total global annual energy consumption at present is 10,537 million tonnes of oil equivalent1 of which the EU consumes 1,715 million tonnes and the USA 2,336 million tonnes.2 Based on current projections, the global annual energy consumption rate will double the current figure by 2050 and triple or perhaps even quadruple by the end of the century. About 85% of the total global energy consumed at present comes from burning fossil fuels, with the proportion approaching 90% for developed countries. The remaining sources of energy are 1 2

1 tonne of crude oil = 42 Giga Joules = 7.3 barrels of oil. 1 Terawatt hour (TWh) = 3.6 × 1015 Joules ; 1 million tonnes of oil produces 4.5 Terawatt hours of electricity (based on 40% efficiency). Data from BP statistical review of World Energy.

What are the true costs of the different energy solutions in terms of human fatalities?

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Table 1.1 Current world and UK usage of different energy sources (GToe and MToe are Giga and Mega tonnes of oil equivalent, respectively). Energy source Coal Oil Gas Total fossil Nuclear Renewables, commercial Biomass, non-commercial

World usage (GToe)

UK usage (MToe)

2.2 3.5 2.2 7.9 0.6 0.6 1–2

40.3 76.1 85.9 202.3 21.3 1.5 Very small

Source: ‘Ingenia’ R. Acad. Eng. Issue 17 (2003).

Table 1.2 World electricity generation from different sources. Source

% of world production

Coal Gas Oil Nuclear Hydro Other (solar PV, wind)

38.1 17.1 8.5 17.2 17.5 1.6

Source: ‘Ingenia’ R. Acad. Eng. Issue 17 (2003).

hydroelectric, nuclear, biomass and other renewables—such as solar, wind, tide, and wave. Table 1.1. shows the current world (and UK) usage of different energy sources while Table 1.2 shows what the main sources of electricity are.

What are the true costs of the different energy solutions in terms of human fatalities? Table 1.3 lists the dangers of different human activities, quantified as loss of life expectancy (LLE) in days. The danger from nuclear energy is significantly less than is often portrayed. Figure 1.1 indicates the human fatalities resulting from different energy sources. When the cost of energy is considered in deaths per TW-year, it is clear that nuclear fission is considerably less dangerous than gas, coal or (especially) hydroelectric energy.

4 Energy … beyond oil: a global perspective Table 1.3 Dangers of different human activities measured in terms of the loss of life expectancy in days for a 40-year old person. LOSS OF LIFE EXPECTANCY Activity of risk

Days LLE

Being male rather than female Heart disease Being unmarried (or divorced) Cigarettes (1 pack/day) Coal mining 30 lbs overweight Alcohol Small cars v. standard size All electric power in US nuclear (UCS) Airline crashes All electric power in US nuclear (NRC)

2,800 2,100 2,000 1,600 1,100 900 130 50 1.5 1 0.03

Source: Professor Bernard Cohen, University of Pittsburgh, Dept. of Physics. (UCS denotes estimate made by the Union of Concerned Scientists while NRC denotes estimate by US Nuclear Regulatory Commission.)

1000 900

Deaths per TW. yr

800 700 600 500 400 300 200 100 0

Coal

Hydro

Gas

Nuclear

Figure 1.1 Deaths per TW.yr (i.e. normalized with respect to the amount of energy generated per year) from different energy supplies. Source: World Nuclear Association.

Fig 1.2 illustrates how nuclear energy puts significantly fewer kilogrammes of CO2 (∼1 %) into the atmosphere, per kWh of energy, than either coal- or gas-fired power stations. Fig 1.3 illustrates how much natural resource is available, when translated into units of Gigatonne of oil equivalent (GTOE) and how use of fast reactor technology multiplies world energy resources by ten. Using fusion technology could be even more efficient would give an even larger resource.

Energy from the Sun 5

1000 900 800 kg CO2/kWh

700 600 500 400 300 200 100 0

Coal-fired power stations

Gas-fired power stations

Nuclear

Figure 1.2 Production of CO2 by different sources of energy for electricity generation. Source: World Nuclear Association.

5000 4500 4000

GTOE

3500 3000 2500 2000 1500 1000 500 0 Coal

Oil

Gas

Uranium Uranium used in thermal used in reactors fast reactors

Figure 1.3 Availability of natural resources worldwide, measured in units of Gigatonne of oil equivalent (GTOE). Source: UKAEA.

Energy from the Sun The Sun lies behind many sources of energy that are available to us. Energy from wind ultimately depends on the heating of the atmosphere by solar radiation, and a combination of gravitational and thermal effects within the atmosphere and ocean

6 Energy … beyond oil: a global perspective

cause winds. Harnessing this kinetic energy of the air is already being realized as an energy source, using wind turbines. The gravitational fields of the Moon and Sun are responsible for causing twicedaily tides in the oceans on Earth. In fact, if the surface of the planet were entirely covered by oceans the amplitude of the tides would only be about 0.4 metres, but the presence and structure of land masses causes tidal amplitudes of over 10 metres. Harnessing the kinetic energy of powerful tidal currents has begun in certain suitable places. Most obviously, the Sun provides solar energy to our planet on an annual basis at a rate of ∼100, 000 TW. Therefore the energy from one hour of sunlight is equivalent to all the energy mankind currently uses in a year.

The nature of the solutions It is not easy to match oil as an energy source: oil itself is cheap, energy-dense, convenient and easy to transport. Getting from renewable primary energy to energy-dense fuels is a particular challenge. It is a challenge to keep aviation and other forms of transport going, given that the production of ethanol from biomass should not be at the price of taking up huge stretches of land with a vast monoculture. The hydrogen economy has been mentioned as a future saviour, but hydrogen is not a primary energy source but rather an energy store. Water is the chemical product of the reaction of hydrogen and oxygen, which of course releases a lot of energy just as does the burning of fossil fuels. But unlike fossil fuels, inter-conversion between water and hydrogen is easily reversible (although energy intensive) so that primary energy sources such as sunlight, the intense heat provided by a high temperature fusion reactor, or indeed electricity generated by any means, can provide sufficient energy to split water into hydrogen and oxygen. Hence the definition of hydrogen as an energy store. We thus obtain a fuel that can be transported. Chemists are responding to these challenges by devising advanced materials that store hydrogen and even by reacting hydrogen with CO2 to get back to hydrocarbons, the energy-dense fuel of choice (and now renewable of course!). In this book Energy . . . Beyond Oil, we consider energy solutions for which the science or technology is proven but still developing: geothermal energy, energy harnessed from the waves and tides (which of course have the advantage of being predictable) as well as energy from wind (we learn that deaths to birds from wind turbines are nothing compared to bird deaths from cats). The cases are presented for the two different types of ‘nuclear’ energy: fission and fusion. Unfortunately the word ‘nuclear’ often causes a knee-jerk reaction among those for whom the terminology simply brings to mind the image of a mushroom cloud. We remind the reader that it is easy to forget that solar energy is nuclear (fusion)

The way forward

7

just as geothermal energy actually arises partly from natural nuclear processes (the radioactive decay of uranium) that take place in the Earth’s core. The case is made that fission, far from being the emblem of a future catastrophe, could instead save the planet. With improvements in reactor design and fuel technology, we have the option of an energy supply that is relatively clean compared to fossil fuel. Fusion is much cleaner still. Fusion as a physical mechanism is well understood: stars have been fuelled by fusion since shortly after the beginning of time. Fusion as a technology requires the dedicated time and talents of engineers and physicists who can mimic Nature and realize the potential of this clean, green, effectively limitless, energy supply. Solar energy is of course harnessing fusion from a distance of 93 million miles. In fact the illuminated Earth receives on average about one kilowatt of power per square metre, easily enough in principle to solve all our energy needs. Photosynthesis—the process by which plants capture solar energy using light sensitive pigments and use this energy to make organic matter from CO2 and water—is indeed the start of the food chain. Yet only a small fraction (less than 1%) of the Sun’s energy is actually trapped and exploited in this way. Much is being done to understand and exploit photosynthesis (such as the specialized production of crops for energy) and to develop ‘artificial photosynthesis’ in which light is converted directly into electricity using solar photovoltaic panels. More straightforward, and widely used, is the direct exploitation of solar hot water panels for domestic heating. In the sunniest of locations it is also feasible to concentrate solar radiation using mirrors (concentrating solar power technology) to provide enough heat to drive turbines for electricity production. The energy alternatives to oil should not be regarded as alternatives to one another, rather it is imperative to consider ‘both . . . and’ rather than ‘either . . . or’. Regardless of how successful we become in energy production, minimizing the various costs and risks is a strong motivation for energy efficiency. All the different energy sources have their advantages and strengths in certain situations; for example, tapping into a particular local energy supply has many advantages for places distant from a large metropolitan area. It is important to offer locally optimal solutions in areas of low population density. Apart from wisdom in optimal resource use, the implementation of a number of energy solutions across any given nation limits the possibility of single-point failures in terms of vulnerability to terrorist attack or distribution breakdown. Security of supply and protection of the environment must remain paramount.

The way forward The question of Energy . . . Beyond Oil brings together scientists of all disciplines: chemistry, physics, biology, materials, engineering, as well as politicians and

8 Energy … beyond oil: a global perspective

industrialists. Not to think about this question is to be in denial about the reality of the severe and looming problems that lie ahead. The costs of alternative energy solutions are dropping, but even so we need increased investment from both private and public sectors, along with government-led incentives, to see us through to the time when fossil fuels are no longer the automatic choice. There are important opportunities for young scientists and engineers—professionals who love challenges and problem solving. Energy . . . Beyond Oil lays out the greatest challenge for this century.

The Authors Professor Fraser Armstrong is Professor of Chemistry in the Department of Chemistry, Oxford and a Fellow of St John’s College. His interests are in inorganic chemistry, biological chemistry, bioenergetics, and in the mechanisms and exploitation of enzymes related to energy production. He has received a number of awards including the European Award for Biological Inorganic Chemistry, the Carbon Trust Innovation Award, the Max Planck Award for Frontiers in Biological Chemistry, and the Royal Society of Chemistry Award for Interdisciplinary Chemistry. He travels widely giving invited lectures on topics including catalysis, bioenergetics, and renewable energy. Dr Katherine Blundell is a Royal Society University Research Fellow and Reader in Physics at Oxford University, and a Science Research Fellow at St John’s College, Oxford. Her interests include extreme energy phenomena in the Universe, for example, around black holes. She is frequently invited to speak at conferences and different institutes around the world and has published extensively on astrophysical jets, relativistic plasmas, and distant galaxies. She has co-authored the book Concepts in Thermal Physics (OUP, 2006) and was recently awarded a Leverhulme Prize in Astronomy & Astrophysics. Professor Ian Fells CBE FREng FRSE is Emeritus Professor of Energy Conservation at Newcastle University. He has published some 290 papers on energy topics as varied as fuel cells, rocket combustion, chemical physics of combustion, nuclear power, and energy economics. He was science advisor to the World Energy Council and to select committees of both Houses of Parliament. He has made over 500 TV and radio programmes and was awarded the Faraday Medal and Prize by the Royal Society for his work on explaining science to the layman. For some publications see www.fellsassociates.com.

2.

Arresting carbon dioxide emissions: why and how? David Vincent Introduction Principles The greenhouse effect Scientific evidence of the existence of climate change Future projections on climate change What atmospheric level of carbon dioxide is ‘safe’? How climate change will affect our lives The UK as an example Developing countries and emerging economies Taking action Technological and policy innovation Summary and conclusions Postscript Resources and further information Some further UK focused reading and sources

9 10 10 11 17 20 22 22 23 25 27 30 32 32 33

Introduction This chapter sets the scene for future chapters covering a range of low carbon technologies from renewables through to nuclear. It reviews how the evidence base for climate change is building up, what the impacts of climate change might be, and how we are beginning to explore the policies and measures which will be needed to make the transition to a low carbon economy. The year 2005 will go down in history as the beginnings of a broad, politicallybacked consensus that man’s activity is influencing our climate. In February 2005, the Kyoto Protocol came into force—binding over 170 countries in action to reduce carbon dioxide emissions, accepted by most informed commentators to be the principal cause of anthropogenically forced climate change. In the same year,

10 Arresting carbon dioxide emissions: why and how?

the G8 group of countries at Gleneagles, Scotland, considered climate change as a key agenda item. Significantly, it set up a forum for discussion with other countries and the emerging economies. The forum, known as the ‘Dialogue on Climate Change, Clean Energy and Sustainable Development’ met for the first time in November 2005. However, the value of the Kyoto protocol is not universally acknowledged. Some argue that although the science underpinning the existence of climate change and the link with carbon dioxide emissions has become unequivocal, the Kyoto protocol is not appropriate for them. A group of these countries, including the US, China, and India (huge emitters of carbon dioxide in their own right) has agreed the need to tackle climate change. Their approach is to promote clean technology development initiatives; though how exactly that partnership will evolve and deliver new low carbon technologies is not, at the time of writing, clear. Nevertheless, whether via the formalized Kyoto Protocol with carbon dioxide emission reduction targets or via other initiatives, a start has been made on the long, uncertain road to a low carbon world. Slowly, but surely, global action on climate change is gathering momentum.

Principles The greenhouse effect The term ‘greenhouse effect’ was first coined by the French mathematician Jean Baptiste Joseph Fourier in 1827. It enables and sustains a broad balance between solar radiation received and Earth’s radiation emitted or reflected. Without that broad balance, temperatures would be about 33˚C cooler and life, as we know it, would not exist. Fig. 2.1 shows how that broad balance arises and is maintained. The sun’s radiation penetrates our atmosphere. Visible and ultraviolet radiation from the high-energy end of the spectrum penetrates most efficiently and directly warms the earth. Re-radiation from the Earth’s surface is mainly from the infrared, lower-energy end of the spectrum radiation, but a significant portion of this radiation is absorbed by certain molecules in the atmosphere that convert it into heat, thereby keeping the earth at temperatures that can support life. Significantly, carbon dioxide is a particularly good absorber of infra-red radiation. In 1859, the British scientist John Tyndall began studying the radiative properties of various gases. He suggested that it was variations in carbon dioxide levels that brought about the various ‘ice ages’ in the Earth’s geological history. The cyclical occurrence of ice ages has been established from analysis of Antarctic ice core samples, with data going back about 800,000 years: temperature variations of between 5–10◦ C are estimated to have occurred. The lower temperatures correspond to ice ages, and the higher temperatures to warm periods such as the one we are experiencing at present. Tyndall attributed these

Principles

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EARTH'S ENERGY BUDGET Reflected by atmosphere 6% Incoming solar energy 100%

Reflected Reflected from by clouds earth's surface 20% 4%

64%

6%

Radiated to space from clouds and atmosphere Absorbed by atmosphere 16%

Absorbed by clouds 3% Conduction and rising air 7%

Absorbed by land and oceans 51%

Radiated directly to space from earth

Radiation absorbed by atmosphere 15% Carried to clouds and atmosphere by latent heat in water vapor 23%

Figure 2.1 The Earth’s energy budget. Source: NASA.

temperature changes to variations in atmospheric carbon dioxide concentrations. Changes in our atmosphere, principally carbon dioxide concentrations, water vapour, and particulates (for example, from volcanic activity), can change the efficacy of the absorption process and hence the temperature of the earth’s surface. In 1896, the Swedish chemist Svante Arrhenius made the first attempt to estimate the effect of carbon dioxide on global average temperatures. Using a simple physical model, he estimated that if atmospheric carbon dioxide concentrations were to be doubled the average global temperature would rise, due to the greenhouse effect, by an estimated 5–6◦ C—an estimate which turned out to be not very different from the most recent model of the Inter-governmental Panel on Climate Change (IPCC) in its Third Assessment Report (IPCC, 2001). Scientific evidence of the existence of climate change The IPCC was established in 1988 by the World Meteorological Office and the UN Environment Programme to assess scientific, technical, and socio-economic information relevant for the understanding of climate change. It said in its Third Assessment Report, published in 2001, that: ‘an increasing body of observations gives a collective picture of a warming world and other changes in the climate system’. The IPCC’s Fourth Assessment Report is due to be published in 2007.

12 Arresting carbon dioxide emissions: why and how?

There is an almost universal scientific consensus that the climate change we are seeing now, and which is beginning to change the natural and economic environments in which we all live, is largely due to human activity. Natural climate change has ebbed and flowed over hundreds of thousands of years with warmer periods interspersed with cooler periods every 12,000 to 20,000 years or so (Fig. 2.2). We also know that these natural changes have been accompanied by changes in atmospheric carbon dioxide levels—around 200 parts per million (ppm) during cooler periods and around 280 ppm during warmer periods. In less than 200 years, human activity has increased the atmospheric concentration of greenhouse gases by some 50% relative to pre-industrial levels. At a little over 380 ppm, today’s atmospheric carbon dioxide concentration is higher than at any time in at least the past 420,000 years. There is no previous human experience of the Earth’s atmosphere at current levels of greenhouse gases to assist us in predicting the consequences. It is likely, though, that the natural

Deep-sea core Ice core Colder/ Warmer/ Colder Warmer more ice less ice 0 Today

Thousands of years ago

200

400

600

Cool cycles

800 Figure 2.2 Glacial cycles of the past 800,000 years. The history of deep-ocean temperatures and global ice volume is inferred from a high resolution record of oxygen-isotope ratios measured in bottom-dwelling foraminifera shells preserved as microfossils in Atlantic Ocean sediments. Air temperatures over Antarctica are inferred from the ratio of deuterium and hydrogen in the ice (McManus, 2004).

Principles

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Departures in temperature (˚C) from the 1961 to 1990 average

0.8

0.4

0.0

–0.4

–0.8 1860

1880

1900

1920

1940

1960

1980

2000

Year

Figure 2.3 Variations in the earth’s surface temperature over the past 140 years since instrumented records began. (IPCC, 2001).

oscillating pattern of ice ages and warm periods is now being disturbed in ways and with impacts we currently do not understand. This massive and rapid rise in carbon dioxide levels is very largely attributed to the burning of fossil fuels to generate energy and to provide transport fuels. Not only is this unprecedented in absolute terms but also the rate of change is faster than has ever been observed before. This rapid change is occurring during a period of human development characterized by massive populations and massive demands on finite resources, including energy. Fig. 2.3 shows direct temperature records back to the middle of the nineteenth century which are considered reliable enough to establish the fact that recent temperatures are warmer than any time since direct measurements began. All of the 10 warmest years have occurred since 1990, including each year since 1995. On 22 October 2005, the UK experienced the highest October temperatures since records began nearly two centuries ago. Fig. 2.4 shows the change in atmospheric concentrations and radiative forcing functions for three of the main greenhouse gases: carbon dioxide, methane, and nitrous oxide. In contrast to natural climate change, anthropogenically forced climate change is a new phenomenon caused, predominantly, by our use of fossil fuels to power developed (and, increasingly, developing) economies. Since the start of the industrial revolution some years ago, we have been increasing the concentration of carbon dioxide and other greenhouse gases in the atmosphere, thickening the greenhouse blanket and beginning the inexorable rise in global temperatures.

14 Arresting carbon dioxide emissions: why and how? (a)

CO2 (ppm)

1.5

Carbon dioxide

360 340

1.0

320 0.5

300 280

0.0

0.5 0.4

1500

0.3

1250

0.2 1000

0.1

750

N2O (ppb)

310

0.0

Radiative forcing (Wm−2)

Methane

1750 CH4 (ppb)

Atmospheric concentration

260

0.15

Nitrous Oxide

0.10 290

0.05 0.0

270 250 1000

1200

1400

1600

1800

2000

Year

200

Sulphur 50

100 25

0 1600

0 1800 Year

SO2 emissions (Millions of tonnes sulphur per year)

Sulphate concentration

(Mg SO42– per tonne of ice)

(b)

2000

Figure 2.4 Global atmospheric concentrations of three of the principal greenhouse gases. (IPCC, 2001).

It took many millions of years to trap carbon chemically in geological strata. Modern man is releasing, in the ‘twinkling of an eye’ relatively speaking, huge quantities of carbon dioxide—with effects we are now beginning to see. Carbon dioxide levels have increased by 31% since 1750. The present atmospheric carbon

Principles

15

dioxide concentration (over 380 ppm—and rising) has not been exceeded during the past 420,000 years and is likely not to have been exceeded during the past 20 million years. The current rate of increase is unprecedented during at least the past 20,000 years. Bearing in mind the historically observed atmospheric carbon dioxide concentration range (around 200–280 ppm), we are, quite simply, in uncharted territory so far as greenhouse gas concentrations and their impacts are concerned. With such a complex subject as climate change, there are areas where our understanding needs to improve—for example, the ‘radiative forcing’ impacts of aerosols and mineral dusts, and the ability of oceans to absorb carbon dioxide. However, we know enough to be sure that global warming over the past 100 years is very unlikely to be due to the variability of natural phenomena alone. In fact, the best agreement between model simulations and observations is found when anthropogenic and natural forcing factors are combined, as shown in Fig. 2.5.

Simulated annual global mean surface temperatures

Anthropogenic: Annual global mean temperatures 1.0 Model Observations 0.5

Temperature anomalies (˚C)

(b)

Natural: Annual global mean temperatures 1.0 Model Observations 0.5 Temperature anomalies (˚C)

(a)

0.0

−0.5

−0.5 −1.0 1850

0.0

1900

1950

−1.0 1850

2000

1900

1950

Year

(c)

(d)

All forcings: Annual global mean temperatures

Simulated global warming 1860-2000: natural and man-made factors

Model Observations

Temperature anomalies (°C)

Temperature anomalies (˚C)

1.0

0.5

0.0

−0.5 −1.0 1850

2000

Year

1.0

Model Observations

0.5

0.0

–0.5 –1.0

1900

1950 Year

2000

1850

1900

Year

1950

2000

Figure 2.5 Comparison of modelled and observed temperature rise since 1860. (IPCC, 2001).

16 Arresting carbon dioxide emissions: why and how?

Figure 2.6 Pasterze glacier around 1900 and in 2000—Kartnen, Austria. (Source: Munich Society for Environmental Research.)

Figure 2.7 Accelerated melting of parts of the Antarctic ice cap. (Source: BBC News website, March 2002.)

It is very likely that the twentieth-century warming has also contributed to a rise in sea levels, through thermal expansion of sea water and widespread loss of land ice. Fig. 2.6 shows an example of glacial retreat and Antarctica provides another example of climate change (Fig 2.7). In summer 2003, as shown in Fig. 2.8, a heat anomaly across Europe was responsible for 26,000 deaths and cost around D13bn. This was closely repeated in 2005. An idea of year-on-year variations is given in Fig. 2.9 which shows summertime temperature data from 1864 to 2003.

1

Principles

a

2

1

4

4

3

3

1

2

17

2 4

2

1

1

1

2

4 3

2

1

0

3

5 –1

2

–2 4

–3 3

2

Temperature anomaly [K]

3 1

2

–4

1

1

Figure 2.8 Localized temperature anomaly—summer 2003. (Schaer et al. 2004.)

Future projections on climate change Looking ahead, what are the likely trends in global temperatures and climate change? Are we going to experience far more severe weather events on a global scale? What will their impacts be? Emissions from fossil fuel burning are virtually certain to drive the upward trend in atmospheric carbon dioxide levels. The IPCC Third Assessment Report projects carbon dioxide levels in the range 490–1260 ppm by the end of this century. Correspondingly, the globally averaged surface temperature is projected to increase by 1.4 to 5.8◦ C over the period 1990–2100 as shown in Fig. 2.10. Of equal importance are projections of changes in global precipitation. On a global scale, water vapour, evaporation, and precipitation are projected to increase. However, at regional levels the various models show both increases and decreases in precipitation. For high-latitude regions precipitation will increase in both summer and winter. Increases in winter precipitation are predicted for northern mid-latitudes, tropical Africa and Antarctica, and increases in summer precipitation are predicted for Southern and Eastern Asia. On the other hand, Australia, Central America, and Southern Africa are projected to show consistent decreases in winter rainfall. The science of modelling climate change is developing all the time; reliability is improving and predictions of likely impacts are becoming more certain. The UK’s

18 Arresting carbon dioxide emissions: why and how?

2003

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1923 σ = 1.28 K T'/σ = 5.3

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Figure 2.9 Distribution of Swiss monthly temperatures for June, July, and August, and seasonal summer temperatures for 1864–2003 (Schaer et al. 2004). The fitted Gaussian distribution is shown as a solid curve. The values in the lower left of each panel list the standard deviation (σ) and the 2003 anomaly normalized by the 1864–2000 standard deviation (T 1 /σ). For summer 2003, the standard deviation was 5.4—which means that it is very unlikely that the temperatures recorded in summer 2003 were within the normal pattern of summertime temperatures for the past 150 years. The European summer temperature trend since 1900 has been rising.

Hadley Centre for Climate Change Prediction and Research at Exeter is widely acknowledged to be among the world’s leading centres of excellence. Conclusions of a symposium in February 2005 entitled ‘Avoiding Dangerous climate change— A Scientific Symposium on Stabilisation of Greenhouse Gases’, were: (i) the pace of climate change exceeded that thought to be the case a few years ago; and (ii) the possibility of more extreme climate change was greater than expected from models developed a few years ago (Schellnuber, 2005).

Principles

(a) 6

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Figure 2.10 Simple model results: (a) global mean temperature projections for the six illustrative Special Report on Emissions Scenarios (SRES) scenarios using a simple climate model tuned to a number of complex models with a range of climate sensitivities. (IPPC, 2001) (b) As for (a) but for a longer timeline.

The effects of anthropogenically forced climate change will persist for many centuries. Emissions of long-lived greenhouse gases (not only carbon dioxide but nitrous oxide, perfluorocarbons, and sulphur hexafluoride) have a lasting effect on atmospheric composition, radiative forcing, and climate. For example,

20 Arresting carbon dioxide emissions: why and how?

Time taken to reach equilibrium

Magnitude of response

Sea-level due to ice melting: several millennia Sea-level rise due to thermal expansion: centuries to millennia

CO2 emissions peak 0 to 100 years

Temperature stabilization: A few centuries CO2 stabilization: 100 to 300 years CO2 emissions Today 100 years

Figure 2.11 2001).

1,000 years

Accumulating impacts of climate change over the long term. (Adapted from IPCC,

several centuries after carbon dioxide emissions occur, about a quarter of the increase in carbon dioxide caused by these emissions is still present in the atmosphere. So even if emissions due to human activity were very significantly reduced over the next 100 years, peaking, say, 30 years from now, carbon dioxide would continue to accumulate over the next 100 to 300 years, and would remain roughly stable for the remainder of the millennium. The long lifetime of carbon dioxide in the atmosphere is, therefore, a significant factor governing climate change impacts. Fig. 2.11 shows how key aspects of climate change will continue to accumulate long after global emissions are reduced to low levels. Temperatures will continue to rise slowly for a few centuries as the oceans continue to warm. Sea level rises will continue for hundreds to thousands of years, due to the continuing impact on ice sheets and the thermal expansion of the oceans. What atmospheric level of carbon dioxide is ‘safe’? There is no straightforward answer to this question—and, indeed, it begs the further question ‘safe for whom—or for what?’. Much depends on our state of knowledge of the possible range of climate change impacts and that, in turn, depends on observed data and modelling projections. In his address to the Royal Institute of International Affairs in October 1998, Professor Michael Grubb, one of the UK’s foremost expert commentators on climate change, said: ‘I believe that policy at present should be guided by the objective of ensuring that we can, if necessary, stabilize atmospheric carbon dioxide concentrations in the range 450–550 ppm

Principles

21

carbon dioxide, which equates to a range of about 500–650 ppm of all greenhouse gases, spanning a range broadly around a doubling of pre-industrial greenhouse gas concentrations.’

In 2002, the Government’s Chief Scientific Adviser, Sir David King, said: ‘If we could stabilise carbon dioxide levels to, say, around 550 ppm (which is around twice pre-industrialisation levels), current models suggest that there would be a significant mitigation of the effects of climate change.’

At the Hadley Centre scientific symposium of 2005, referred to above, there was much cause for concern. The international scientific community on climate change reported a succession of observed and predicted changes to our climate. The full report of the symposium was published in January 2006. Observed changes reported include: (i)

0.6◦ C rise in annual average global temperatures;

(ii)

1.8◦ C rise in Arctic temperature;

(iii)

90% of Earth’s glaciers retreating since 1850;

(iv)

increased freshwater flux from Arctic rivers appears to be already at 20% of the levels which are estimated would cause shutdown of thermo-haline circulation (THC);

(v) Arctic sea ice reduced by 15–20%. Predicted changes included: (vi)

at around 1.5◦ C rise above pre-industrial temperatures, we could see an onset of complete melting of Greenland ice—causing, when complete, about 7 m of additional sea level rise;

(vii)

at around 2–3◦ C rise above pre-industrial temperatures (equivalent to about a doubling of atmospheric carbon dioxide concentrations) we could see the conversion of terrestrial carbon sink to carbon source, due to temperature-enhanced soil and plant respiration overcoming CO2 enhanced photosynthesis. This could result in desertification of many world regions as there is predicted to be widespread loss of forests and grasslands, and accelerating warming through a feedback effect. We could also begin to see the collapse of the Amazon rainforest, replacing forest by savannah with enormous consequences for biodiversity and human livelihoods.

22 Arresting carbon dioxide emissions: why and how?

(viii)

at around 5◦ C rise above pre-industrial temperatures (towards the upper end of the estimates in the IPPC’s Third Assessment Report) symposium experts predicted a 50% probability of thermo-haline circulation shutdown. Under this scenario the melting of the Greenland ice sheet and the West Antarctic ice sheets may interact with the climate in ways that we have not begun to understand.

On the basis of our best knowledge and understanding today, we can see that the consequences of greenhouse gas emissions rising to beyond 550 ppm (the doubling of concentrations compared with pre-industrial levels) could be very serious indeed.

How climate change will affect our lives The UK as an example The UKCIP (UK Climate Impacts Programme) was established in April 1997 to help UK organizations assess and prepare for the impacts of climate change. UKCIP is an independent activity based at the University of Oxford’s Environmental Change Institute. It is a highly respected source of impartial and objective analysis and information on climate change as it is likely to impact on the UK. Its report, Climate Change Scenarios for the United Kingdom, was published in 2002 (UKCIP, 2002). More extreme weather events are becoming a feature of the changing climate in the UK. Although no single extreme weather event can be put at the door of climate change per se, events taken together, over time, align well with the kind of trends which the climate change models predict. TV and media coverage of the flooding in Boscastle in 2004, in Carlisle at the beginning of 2005, and of tornadoes in Birmingham in summer 2005 have faded from the media but they are very much a live issue for those people directly affected. UKCIP studies indicate that climate change could have far reaching effects on the UK’s environment, economy, and society. Without deep cuts in emissions, average temperatures could rise by about 3◦ C by 2100 bringing with it more variable and more extreme weather events. It is worth putting this temperature rise in context. By the 2040s or so, on current trends, UKCIP considers that the ‘anomolous’ summer 2003 temperatures will be the norm; and by the 2080s, the summer 2003 temperatures could be regarded, relatively speaking, as being on the cool side. Rainfall could increase by as much as 10% over England and Wales and 20% over Scotland by the 2080s. Seasonal changes are expected, with models suggesting that UK winters and autumns will get wetter, and that spring and summer rainfall patterns will change so that the north west of England will be wetter and the south east will be drier. Of course, individual years and groups of

How climate change will affect our lives

23

years will continue to show considerable variation about this underlying trend. However, the frequency of extreme weather events, such as severe floods, is more likely to increase than decrease. It is less clear at the moment how the frequency of storms and high winds could be affected by climate change. Some striking evidence of the increase in frequency of climate-change-related events concern the Thames Barrier which was opened in 1983. The last tidal flood of great significance in London occurred in 1928. However, in response to increased awareness of the risk of tidal flooding up the Thames, it was decided to construct the Barrier. At the time of its design in the 1970s, it was expected that it would be used once every few years. In practice, the Thames Barrier (see Fig. 2.12) has been used 6 times a year, on average, over the past 6 years—a clear measure of the increased storm surge levels on the eastern coastline of England. Developing countries and emerging economies Developing countries are in the front line so far as the adverse impacts of climate change are concerned. Fig. 2.13 from the IPCC Third Assessment Report shows the results of modelling of global temperature changes over the period 2071–2100 compared with 1961–90. In his foreword to the report ‘Up in Smoke’, (IIED, 2004), Dr R. K. Pachauri (Chairman of the IPCC) said: ‘The impacts of climate change will fall disproportionately upon developing countries and the poor persons within all countries, thereby exacerbating inequities in health status and access to adequate food, clean water and other resources.’

We have seen examples of extreme weather events and the beginnings of trends— for example, in rainfall—which will be crucial to the future existence of millions of the poorest, most vulnerable people on earth. The report, published in October 2004, describes the plight of poor farmers in the tropical and subtropical areas of the world. They depend on rain-fed agriculture and are barely able to achieve a subsistence level of existence. Variations in precipitation levels, degradation of soil quality, and increased frequency of extreme weather conditions could make the lot of poor peasants far more difficult—even more so than it is today. Some populations will seek to migrate to areas where the environmental conditions are more likely to sustain them. How this migration might impact on neighbouring lands and their peoples is open to question. The significance of climate change on the geo-political stability of many parts of the world is only just beginning to be recognized. Included in the group of developing countries are some of the fastest growing economies—China, India, Brazil, Mexico, and Russia. They are fuelling their economic development with coal and other fossil fuels. They are emitting carbon dioxide at a rate which is exacerbating the upward trend in atmospheric carbon

24 Arresting carbon dioxide emissions: why and how?

(a)

Annual Closure of Barrier

(b)

19 85 19 86 19 87 19 88 19 89 19 90 19 91 19 92 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02

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The number of closures of the Thames Barrier in each year

Number of Thames Barrier closures against tidal surgess, 1983–2002

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Figure 2.12 (a) The Thames Barrier, downstream of London, which is closed during tidal surges. (b) Graph showing number of Thames Barrier closures over the period 1983–2002. Source: the Environment Agency.

dioxide concentrations. On current trends, China, for example, is set to overtake the US as the largest global carbon dioxide emitter within the next 10 years. By 2030, it is estimated that coal plants in developing countries could produce more carbon dioxide emissions than the entire power sector of OECD countries does now.

Taking action

25

8

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Figure 2.13 Modelling the annual mean change of the temperature in ◦ C (shading) and its range (contours of constant temperature) (Unit: ◦ C) for the period 2071 to 2100 relative to the period 1961 to 1990. Source: IPPC, 2001.

Taking action It is clear that the climate is changing—for all living things on earth. We are moving into uncharted territory so far as the impacts on flora and fauna, people and businesses, and countries and global regions are concerned. We can, and should, take action now to move to a low carbon global economy. If we start

26 Arresting carbon dioxide emissions: why and how?

now, we stand a chance of achieving the huge cuts in greenhouse gases required over the decades ahead and, hopefully, of avoiding the worst impacts of climate change in the centuries ahead. If we take insufficient action, future generations will find it much more difficult to halt, and subsequently reduce, atmospheric greenhouse gas levels and there will be significant changes to their environments, to food growing areas of the world, and to patterns of human migration. We can all take action to cut out energy waste, buy energy efficient equipment and products, and reduce the amount of high-carbon energy we buy. However, in order to make a material impact, individual actions need to be encouraged and consolidated into national, and global, action. Creating effective policies and measures to mediate the transition to a low-carbon economy is the role and responsibility of Governments—all Governments. In developed countries it means governments working with business, the public sector, and individuals, to set up programmes that encourage and support action and investment to improve energy efficiency and to reduce the carbon intensity of economic activity. The scale of global activity required to halt and reduce greenhouse gas emissions to around 60% by the middle of this century is huge. A sense of the scale involved can be seen from the work of Robert Socolow and his colleagues at Princeton University, USA (Socolow, 2004). They have developed the concept of stabilization wedges. A wedge represents an activity that reduces emissions to the atmosphere, starting at zero today and increasing linearly until it delivers around 1 Gt carbon/year of reduced carbon emissions in 50 years’ time. It thus represents a cumulative total of 25 Gt carbon of reduced emissions over 50 years. A number of nations have started their own climate change programmes. The UK Government’s Climate Change programme, launched in 2000, is an example of early action at the national level designed to show leadership, achieve Kyoto obligations, and make progress towards a domestic goal of a 20% reduction in carbon dioxide emissions by 2010 based on 1990 levels (DETR, 2000). The UK Government’s Energy White Paper of 2003 confirmed that climate change is central to its environment and energy policies (DTI, 2003). It accepted the Royal Commission on Environmental Pollution’s recommendation, in its 2000 report on the changing climate, that the UK should put itself on a path towards a reduction in carbon dioxide emissions of some 60% from current levels by about 2050 (Royal Commission, 2000). For business, the public sector, and individual consumers it means accepting and being part of, the transition to a low-carbon economy: cutting out energy waste; investing in and preferentially purchasing lower carbon intensity heat and power; and making choices which reduce the carbon footprint of economic, social, and leisure activities. Much can be achieved with today’s technology and know-how. Therefore, a considerable part of the UK’s Climate Change programme has been focused on creating incentives for investment in

Taking action

27

energy efficiency measures and the deployment of commercial sources of lowcarbon electricity. Raising awareness about climate change in the respective consuming sectors of the economy is an essential pre-requisite to taking action. Individual consumers have a mixed perception of climate change and their own roles and responsibilities to reduce carbon dioxide emissions. Some, not many, are aware and have adjusted their purchasing decisions accordingly. The majority, however, have demonstrated by their purchasing behaviour that they: (a) do not understand their impact on carbon dioxide emissions; (b) or do not understand how to reduce their carbon dioxide emissions; (c) or do not care. There is a huge challenge to raise consumer awareness, change behaviours, and stimulate action. The same, generally speaking, applies to the business community, though like domestic consumers there are leaders and laggards. Corporate business, thought of by some as being in the ‘problem’ rather than the ‘solution’ camp, is showing that not only is it aware of climate change and the impacts it is beginning to have, but is also keen to be pro-active. Thirteen major UK and international companies offered to work in partnership with the Government towards strengthening domestic and international progress on reducing greenhouse gas emissions. A key quote from their letter to Prime Minister Tony Blair in May 2005 (Corporate Leaders Group on Climate Change, 2005) is: ‘Enabling a low-carbon future should be a strategic business objective for our companies and UK plc as a whole’. Canadian corporate leaders wrote a similar letter to Canadian Prime Minister Paul Martin in November 2005 (Canadian Executive Forum on Climate Change, 2005). Their opening paragraph said: ‘As corporate leaders representing a broad cross-section of the Canadian economy, we believe that all governments, corporations, consumers and citizens have responsibilities under the Kyoto Protocol and that the world must act urgently to stabilize the accumulation of greenhouse gases in the atmosphere and minimize the global impacts of climate change.’

Making the transition to a low-carbon future will require not only widespread systematic deployment of the best of today’s technology, but also a concerted effort to innovate, develop, and commercialize new low carbon and energy efficient technologies. The huge reductions in carbon dioxide emissions that are required will not be achieved without developing and deploying energy efficiency and low carbon technologies at scale in existing and emerging economies, and as part of a global endeavour. What is required is no less than a global approach to developing and commercializing a new generation of low carbon technologies and products. The power and innovation of multi-national energy companies, technology companies, and the investor communities need to be harnessed and encouraged to achieve the low-carbon economy goal. This will not happen unless the right business environment can be created. Helping the

28 Arresting carbon dioxide emissions: why and how?

market to deliver huge reductions in carbon dioxide emissions at scale and on the desired timescales, whilst maintaining and improving economic and social wellbeing, requires intervention by and cooperation between governments, and between governments and business. Making the transition from fossil fuel, highcarbon investment to low-carbon, sustainable (environmentally, socially, and commercially) investment, requires a common sense of purpose and recognition that it makes business sense to do so. Accelerating the commercialization of new and emerging low carbon technologies is crucial to achieving a timely transition to a low carbon economy.

Technological and policy innovation Over the last 100 years or so, there have been many examples of technological innovation: ‘cats eyes’ on roads and motorways worldwide; television; mobile phones; etc. These are very different technologies but, like many global scale innovations, both have changed the everyday lives of millions of people. Energy supplying and consuming technologies pervade the lives of billions of people in the developed, and increasingly in the developing, world. Making sure there are efficient, affordable and reliable low-carbon solutions to our energy needs is part and parcel of the transition to a low-carbon economy. However, that transition will not happen overnight. It took 100 years from the earliest heavier-than-air–machine, skimming a mile or so over that windswept North American landscape in 1903, to the modern aeroplane fleets and, importantly, the international airline infrastructure, to mature to a commercial, affordable, and (in the main) efficient service. Furthermore, the pace of development was accelerated by two world wars which gave a huge impetus to aircraft and engine design innovation. The energy sector is one where price, demand, and the strength—or otherwise—of government intervention impact significantly on the pace of innovation and commercialization. 2005 was the year in which the $60/barrel of oil came into existence. Whether this was simply a short term reaction to current political and economic uncertainties, or a trend-setting market reaction to future supply availability in a world with rapidly growing demands for energy, nobody really knows for sure. Short term price fluctuations have been a characteristic of world energy markets for decades. However, when price fluctuations become an upward trend, it drives the search for new energy sources and new energy technologies—for example, the exploration and production of oil from reserves which are increasingly more costly to exploit but which are, nevertheless, profitable investments. Another driver for new and emerging energy technologies and low-carbon technology innovation is the finite nature of our oil and gas reserves. Some

Technological and policy innovation

29

independent oil consultants suggest that at present rates of consumption and discovery, world oil production will peak between 2015 and 2020. Predictions of production peaks and their timings are, however, fraught with dispute and controversy. What is not in dispute is that demand for energy is rising—driven by the emerging economies. These factors are strong economic drivers to explore for more reserves and to seek alternatives to oil for energy supplies. Many countries are looking at which new and emerging low carbon technologies make climate change and business sense to them. In 2002, as part of a UK government-commissioned study to examine the long-term challenges for energy policy (Performance and Innovation Unit, 2002), the government’s Chief Scientific Adviser, Sir David King, led a review of energy research in the UK. The conclusion (Energy Research Review Group, 2002) was that there were six areas of research in particular where there was significant headroom between where the technology is today and where it could be if more research, development and demonstration (RD&D) were supported. These included: carbon capture and storage, which might enable us to continue to burn fossil fuels by collecting the carbon dioxide and sequestering it safely in suitable geological formations for the long term; energy efficiency gains across the energy consuming sectors; hydrogen production, distribution, use, and storage; nuclear fission and radioactive waste management; materials for fusion reactors; and renewable energy technologies including, in particular, solar photovoltaics, wave and tidal. To coordinate energy R&D in the UK, the government set up the UK Energy Research Centre (UKERC) in 2005, and in his Budget 2006, the Chancellor announced the formation of what is now called the Energy Technologies Institute– a public-private partnership to support RD&D into energy and low-carbon technologies. Energy markets, and their shaping by policies, priorities, and events, are also crucial factors. In the UK, for example, the energy generators, network operators and suppliers are part of a privatized, regulated industry in what is one of the most liberalized energy markets in the world. The degree of regulation and liberalization, coupled with government policies of the day and public opinion, are the main determinants of the climate for energy technology innovation. Thus, for example, increasing the percentage of low-carbon electricity from the UK supply system and decentralized sources, depends not only on government policies on clean coal, carbon capture and storage, and nuclear power, but also, in part, on the extent to which there are incentives for grid owners to invest in the necessary new transmission and distribution lines to bring low-carbon power to consumers. At the heart of the issue are questions of the type raised by the UK Energy regulator (Ofgem), government, and informed commentators:

30 Arresting carbon dioxide emissions: why and how?

(i)

whether, and to what extent, a liberalized market can provide sufficient stimulus for low-carbon technology (including the infrastructure) innovation and hence deliver a low-carbon economy; and

(ii)

if government intervention is needed, what form should it take, who needs to be encouraged, and for how long should the intervention measures operate.

Multinational energy technology companies will respond to the different market opportunities according to their overall attractiveness and strategic value. They have the capacity and the market position to capitalize on innovation— either ‘home-grown’ or acquired from bought-out, smaller companies. They will dominate the development of standardized energy technologies. The race to develop and deliver standardized, communicating products to global scale markets (sometimes regulated, sometimes less so) will be a driving strategy. Countries like the UK, representing only a few percent of global demand, will not, individually, present large enough markets to influence the nature and direction of innovation for the bulk energy supply technologies of the future. Conversely, making one-off ‘specials’ to fit a particular national standard or specification will be supplied but at premium rates. Much has been written about technological innovation and the roles of the market and the State. Academic papers, theories, and models abound. One is the work carried out by the Environmental Policy and Management Group (EPMG) at Imperial College, London. Their research focuses on how to develop better policy processes to promote sustainable innovation for achieving social, environmental, and economic goals. In the following chapters, there are descriptions of a range of low carbon technologies and concepts—from nuclear fusion through carbon capture and long term storage, to novel photovoltaic devices. Energy efficiency technologies, designs, and products are also covered. So often, reducing demand and cutting out energy waste is either forgotten or ignored. And yet it is an important step in the process of decarbonizing economies, improving resource productivity, and saving money. The energy supply side is regarded by many as where the exciting action is—for example, smart science and engineering, market-driven technological innovation, large construction projects, etc. Energy efficiency is regarded as boring by some, ineffective by others. In fact, the technological, attitudinal, and behavioural challenges on the demand side are just as challenging as they are on the supply side. Energy efficiency savings are a reality not a myth. Through procurement decisions based on whole life costs and a carbon life cycle analysis, backed up by a higher standard of energy management, it is possible to make significant energy savings using today’s know-how. Savings in demand

Summary and conclusions

31

of the order of 20–30% are not considered to be unreasonable (Performance and Innovation Unit, 2002). There are opportunities everywhere in industry, business, transport, and the public and domestic sectors, with building and transport providing particularly important opportunities.

Summary and conclusions In this chapter, the greenhouse effect has been described, and the growing body of scientific evidence supporting the existence of anthropogenically forced climate change has been summarized. The link between global temperature rises and greenhouse gas emissions (particularly carbon dioxide from the combustion of fossil fuels) has, for most informed people, been demonstrated beyond reasonable doubt. Examples from the growing body of weather phenomena have been quoted as being indicative, not predictive, of the kind of weather events which we might experience more of in the decades to come. The pace of anthropogenically forced climate change is faster now than we thought just a few years ago. What we are seeing may be ‘benign’ compared with the frequency and intensity of weather events to come. There are still uncertainties to be explored. However, as computing power develops and more data is gathered it will be possible to develop and test the ever-increasingly complex scientific models required to improve our understanding of climate change and its impacts. The general response from many developed countries to anthropogenically forced climate change has been to ratify the Kyoto Protocol—a first global step to reducing carbon dioxide emissions and tackling climate change. Other countries, including the US, China, and Australia, are exploring other ways to collaborate on cleaner and low-carbon technologies. In the UK, the government has a goal to reduce carbon dioxide emissions by 20% by 2010 on 1990 levels. It also has a longer term aspiration to reduce them by some 60% by around 2050 based on 1997 levels. The scale of reduction is regarded as not just a UK goal, but a global one. They are not targets or end games in their own right. They are markers on the road to a low-carbon economy. What concentration of greenhouse gases in the global atmosphere is ‘safe’ is, to be honest, unknown. Developing countries are at a stage when energy consumption, economic growth (from a relatively low base), and standards of living are inextricably linked. Using the cheapest source of energy is the only option available to them, and this often means using indigenous fossil fuels, thereby forcing carbon dioxide emissions upwards. Paradoxically, they are also at the ‘sharp end’ of extreme weather events associated with anthropogenically forced climate change. Making the global transition to a low-carbon economy is therefore particularly important for developing countries.

32 Arresting carbon dioxide emissions: why and how?

Developed countries are beginning to create energy choices that include low carbon technologies. However, the nature, direction, and pace of innovation of technologies for historically low-risk, relatively low-return utilities is heavily dependent on the degree of intervention from governments and the regulatory authorities (where energy markets have been liberalized). No single technology or concept will achieve the global goal of tackling anthropogenic climate change. No single policy approach will yield success. The solutions for developed countries seeking to decarbonize their established economies from an established fossil fuel base, will be different from those of developing countries seeking to raise standards of living, gain a foothold in the global economy, and take action to avoid the worst impacts of the extreme weather events and climate trends to which they are particularly vulnerable. Both mitigation and adaptation strategies will be required. On mitigation, we know that today’s technologies will help us make a start towards decarbonizing our economies, but they will not be sufficient. Innovation to develop and deploy a new generation of low-carbon supply and demand side technologies will be essential. Innovation—and commercialization—will not happen at the pace and on the scale required, unless governments and markets work to create a framework which provides incentives to stimulate the necessary investment in, and to expand the necessary customer base for, low carbon technologies and products.

Postscript Since this chapter was written in the first half of 2006, the UK Government’s Energy Review and the Stern Review on the Economics of Climate Change have been published. The Energy Review, published in July 2006, put forward proposals for tackling the huge energy and climate change challenges we face, at home and abroad (Energy Review, 2006). The Stern Review, the first major review of the economic implications of climate change, was published in October 2006. This review painted an economist’s picture of the costs of taking action to tackle climate change and the far bigger costs if we fail, globally and collectively, to take action in the next decade. In summary, the Stern Review concluded that: ‘The costs of stabilising the climate are significant but manageable; delay would be dangerous and much more costly. Action on climate change is required across all countries, and it need not cap the aspirations for growth of rich or poor countries.’

In these few words, the value proposition for humanity is clearly expressed. Start now to invest in the transition to a low-carbon economy and we stand a better chance of a viable future for tomorrow’s generations. Prevaricate and

Resources and further information

33

we face an increasingly higher probability that climate change will become irreversible and change the course of our world forever. The choice, surely, is unequivocal.

Resources and further information Canadian Executive Forum on Climate Change, 2005. Open letter to the Canadian Prime Minister from the Executive Forum on Climate Change Call to Action on Climate Protection, Energy and Sustainable Development, dated November 2005. Corporate Leaders’ Group on Climate Change, 2005. Open letter to the Prime Minister from HRH The Prince of Wales’s Business & the Environment Programme Corporate Leaders’ Group on Climate Change, dated 27 May 2005. Department of the Environment, Transport and the Regions, (DETR) 2002. Climate Change – The UK Programme, Department of the Environment, Transport and the Regions, London. DTI, 2003. The Government’s Energy White Paper of 2003: Our energy future creating a low-carbon economy. Available from www.dti.gov.uk/publications Energy Review Report, 2006, The Energy Challenge, Department of Trade and Industry, published July 2006. Environmental Policy and Management Group, Imperial College. Transforming policy processes to support sustainable innovation: some guiding principles: www.imperial. ac.uk/environmentalscience/research/epmg/EPMGFrontpage.html www.iccept.ic.ac. uk; and on the Economic and Social Research Council’s sustainable technologies programme at: www.sustainabletechnologies.ac.uk. Foxon et al., 2005. Transforming policy processes to support sustainable innovation: some guiding principles. Environmental Policy and Management Group, Imperial College, www.imperial.ac.uk/environmentalscience/research/epmg/EPMGFrontpage.html www.iccept.ic.ac.uk; and on the Economic and Social Research Council’s sustainable technologies programme at: www.sustainabletechnologies.ac.uk. International Institute for Environment and Development (IIED) and the New Economics Foundation, 2004. Up in Smoke: threats from and response to the impacts of global warming on human development. www.neweconomics.org. The Intergovernmental Panel on Climate Change (IPCC) 2001. Third Assessment Report. Available from the IPCC website www.ipcc.ch McManus, 2004, Glacial cycles of the past 800,000 years. Nature, 429, 623–28. Royal Commission on Environmental Pollution’s 22nd report, 2000. The Changing Climate www.rcep.org.uk/newenergy.html Schaer et al. 2004. Localised temperature anomaly–summer 2003. Nature, 427, 332–36. Schellnuber, J. (ed) 2005. Avoiding Dangerous climate change–A Scientific Symposium on Stabilisation of Greenhouse Gases. 1–3 February, 2005 at the Hadley Centre for Climate Prediction and Research, the Met Office, Exeter, United Kingdom. Socolow, J. 2004. Stabilization wedges: solving the climate problem for the next 50 years with current technologies. Science, 305. www.sciencemag.org

34 Arresting carbon dioxide emissions: why and how?

The Performance and Innovation Unit’s Energy Review– a report to Government published in February 2002. The Chief Scientific Adviser’s Energy Research Review Group review of energy R&D– 2002 available from www.ost.gov.uk The Stern Review, 2006, The Economics of Climate Change. UKCIP, 2002. The UK Climate Impacts Programme Climate Change Scenarios for the United Kingdom, 2002. The UKCIP02 Scientific Report April 2002. Available from: www.ukcips.org.uk

Some further UK focused reading and sources The Climate Change Challenge 1: Scientific evidence and implications–a Carbon Trust publication available from www.thecarbontrust.co.uk Climate Change and the Greenhouse Effect–a briefing from the Hadley Centre, Met. Office: www.metoffice.gov.uk/research/hadleycentre/. Hadley Centre for Climate Prediction and Research–www.hadleycentre.com. The Hadley Centre is the UK Government’s centre for research into the science of climate change. Tyndall Centre for Climate Change Research-www.tyndall.ac.uk. The Tyndall Centre, funded by three UK research councils, is the national centre for trans-disciplinary research on climate change. The UK Energy Research Centre–www.ukerc.ac.uk

The author Dr David Vincent is Technology Director of the Carbon Trust, a private company set up by the UK Government in response to the threat of climate change to accelerate the transition to a low-carbon economy. He trained as a chemical physicist and, motivated by the energy crises of the early 1970s, decided to pursue a career in the energy field. He has held a variety of posts in UK Government Departments focusing on energy efficiency and low-carbon technology RD&D, and energy/climate change policy development. His interests include lowcarbon technology innovation and commercialization and the interaction between Governments and markets to drive low-carbon choice and investment.

3.

Geothermal energy Tony Batchelor and Robin Curtis Introduction High-temperature resources Hot dry rock or enhanced geothermal systems Medium-temperature resources Geothermal energy as a sideline of oil and gas industries Low-temperature systems with heat pumps Potential for future growth Conclusions Acknowledgements Resources and further information

35 38 39 41 43 43 45 46 46 46

Introduction The term ‘geothermal energy’ describes all forms of heat stored within the Earth. The energy is emitted from the core, mantle, and crust, with a large proportion coming from nuclear reactions in the mantle and crust. It is estimated that the total heat content of the Earth, above an assumed average surface temperature of 15◦ C, is of the order of 12.6 × 1024 MJ, with the crust storing 5.4 × 1021 MJ (Armstead, 1983). Based on the simple principle that the ‘deeper you go the hotter it gets’, geothermal energy is continuously available anywhere on the planet. The average geothermal gradient is about 2.5–3◦ C per 100 metres but this figure varies considerably; it is greatest at the edges of the tectonic plates and over hot spots–where much higher temperature gradients are present and where electricity generation from geothermal energy has been developed since 1904. Geothermal energy is traditionally divided into high, medium, and low temperature resources. Typically, temperatures in excess of 150◦ C can be used for electricity generation and process applications. Medium temperature resources in the range 40◦ C to 150◦ C form the basis for ‘direct use’ i.e. heating only, applications such as space heating, absorption cooling, bathing (balneology),

36 Geothermal energy

Power production Heating or cooling Direct use Loops

12˚C ~100 m

Reinjection wells Production wells

(1500 m–3000 m)

Reinjection Production

1000 m–2000 m 40˚C–150˚C

~190˚C–300˚C

Figure 3.1 Cartoon showing the basic principles of extracting geothermal energy.

process industry, horticulture, and aquaculture. The low-temperature resources obtainable at shallow depth, up to 100–300 metres below ground surface, are tapped with heat pumps to deliver heating, cooling, and hot water to buildings. The principles of extracting geothermal energy, in applications ranging from large scale electrical power plants to smallscale domestic heating, are illustrated in Fig. 3.1. Geothermal energy can be utilized over a temperature range from a few degrees to several hundred degrees, even at super critical temperatures. The high temperature resources, at depth, are typically ‘mined’ and are depleted over a localized area by extracting the in situ groundwaters and, possibly, re-injecting more water to replenish the fluids and extract more heat. Although natural thermal recovery occurs, this does not happen on an economically useful timescale. On the other hand, the low temperature resources can be designed to be truly renewable, in the sense that the annual rate of extraction can be designed to be matched by the rate of recovery. Where warm water emerges naturally at the Earth’s surface, man has probably used geothermal energy since prehistoric times. On a commercial scale, electricity generation using geothermal energy is now over 100 years old, with 24 countries having plants on line. Direct use and heat pump applications are recorded for over 70 countries. It is not generally appreciated that geothermal energy currently ranks fourth in the league table of ‘alternative’energy sources in terms of energy delivered—after biomass, hydropower and, very recently, wind (REN21, 2005).

Introduction

37

Geothermal energy has five key characteristics that can deliver important benefits as an energy source supplying heat: •

It provides a very large resource base, readily available in one form or another in all areas of the world.

•

It is a reliable and continuous source of energy and can provide base load electricity, heating, cooling, and hot water in the right circumstances. There is no intermittent nature to the resource.

•

The technology is maturing and geothermal energy can be economically competitive as long as applications are designed correctly and are matched to geological conditions.

•

It can leverage the role of other forms of renewable or carbon-free electricity by factors of three to four when used with heat pumps in heating and air conditioning applications; i.e. one unit of electrical power can deliver four units of carbon free heat.

•

It is already accepted in various sectors of the market place both for investment and operations, although the technologies are not yet understood by a wide audience.

In the context of this book, two additional features of geothermal energy should be highlighted. •

If the world moves towards a hydrogen economy, there will be a need for nonfossil fuel sources to provide the energy for hydrogen production from water. Given that geothermal energy is ideal for operation at a steady base load, but cannot in itself be transported long distances, it can form an excellent basis for hydrogen production—with the hydrogen itself then being transported to point of use. This already forms part of the Icelandic proposals to become the first hydrogen based economy in the world (Sigfusson, 2003).

• At the low-temperature end of the spectrum, the fortuitous role of geothermal

direct use or geothermal heat pumps in matching the temperature requirements for the heating and cooling of buildings, presents one of the few currently available options for eliminating the use of fossil fuels (and their resulting carbon emissions) as the dominant energy source for providing thermal comfort in buildings. The reader who wishes to go beyond the discussion presented here is referred to the online article by Dickson and Fanelli (see web resources below) which is drawn from their UNESCO publication (Dickson and Fanelli, 2003), or

38 Geothermal energy

the excellent review paper in Renewable and Sustainable Energy Reviews (Barbier, 1997).

High-temperature resources Fig. 3.2 shows the 24 countries that had established installations for geothermal electrical power generation in 2005. Typically, the high-temperature geothermal industry uses geothermal fluids from the ground at 200◦ C to 280◦ C from wells 1,500 to 2,500 metres deep. This type of resource is only found in regions with active volcanism and tectonic events on major plate and fault boundaries. The highest grade of geothermal energy is dry steam; it only occurs in rare and geographically limited locations where the in situ fluids can exist as steam (for example, the Geysers, California and Larderello, Italy) and can be fed directly to turbines. More commonly, however, the fluids are held in the rock as hot, pressurized liquids that can convert spontaneously to steam at the surface to drive turbines. In lower temperature systems and systems with difficult chemistry conditions, the geothermal fluids are fed to heat exchangers where a secondary circuit heats a closed, clean fluid that is used to power a turbine or rotary expander. These latter systems will become more important as the use of lower temperature resources is increased (DiPippo, 2005).

Location of Geothermal Power Sites, 2005 Germany Austria Iceland 202 MWe 0.2 MWe 1 MWe

Italy 790 MWe

Turkey 20 MWe

Russia 79 MWe

USA 2544 MWe

China 29 MWe Japan 535 Mwe Thailand 0.3 MWe Philippines 1931 MWe Papua New Guinea 6 MWe

Mexico 953 MWe Guatemala 33 MWe EI Salvador 151 MWe Nicaragua 77 MWe

New Zealand 435 MWe

Costa Rica 163 MWe Guadeloupe Azores 15 MWe 16 MWe

Kenya 127 MWe

Ethiopia 7 MWe

Indonesia 797 MWe

Australia 0.2 MWe

TOTALS Installed 2000: 7,974 MWe, and 2004: 8,912 MWe (Generated 56,798 GWh/y) © Tony Bachelor, 2005

Figure 3.2 Map showing location of the principal regions of high-temperature geothermal power production. Note that MWe denotes Mega watts of electricity as distinct from MWt (Mega watts of heat energy).

Hot dry rock or enhanced geothermal systems

39

10000 9000

MWe installed capacity

8000 7000 Rate of Increase from 1980: 203 MWe/year

6000 5000 4000 3000 2000 1000 0 1970

1975

1980

1985

1990 Year

1995

2000

2005

2010

Figure 3.3 Growth in installed capacity of electricity generation from geothermal energy.

In 2004, the reported installed generation capacity was 8,912 MWe , generating 56,798 GWh of electricity per annum—an average availability of 72%. Fig. 3.3 shows the sustained growth rate in installed capacity of 203 MWe year, a steady capital expenditure of close to $1 billion per annum. The overall fraction of geothermal power generation compared to the world total power generation is currently 0.4% and the goal of the geothermal community is to raise that fraction to 1% by 2010. However, the apparently small global fraction masks the local importance of geothermal power production. Fig. 3.4 shows the importance of indigenous geothermal power to certain developing countries; it is worth noting that geothermal power is economically competitive with hydropower (for example, Central America and New Zealand) under the right circumstances. A detailed worldwide assessment of the state of geothermal electricity production, reviewed following the 2005 World Geothermal Congress is available (Bertani, 2005).

Hot dry rock or enhanced geothermal systems Given the concept of ‘the deeper you go the hotter it gets’, the ‘blue skies’ aspiration of the geothermal industry has been the Hot Dry Rock (HDR) concept— now also referred to as Enhanced Geothermal Systems. With the resource available everywhere, the goal is to drill to the required depth (temperature)

40 Geothermal energy

30 25 20 15 10 5

ua ra g

N ic a

R ic a ta

C os

el an

d

s Ic

in e ilip p

Sa

Ph

lva d

ib e /T EI

C hi na

Ke ny a

or

0 t

% of National Energy Delivered

35

Figure 3.4 Utilization of geothermal energy in Iceland and some developing countries.

to engineer a large permeable heat transfer surface between one or more wells, to inject cold water at depth and to recover it at temperatures suitable for the production of electricity. Three major research projects have been undertaken in this technology, at Los Alamos, USA in the 1970s and 1980s, in Cornwall in the UK in the 1980s and 1990s, and currently at Soultz in France. Other research and development work has also been undertaken in France, Sweden, Germany, and Japan. Pro-commercial projects are now underway in Switzerland and Australia. The HDR concept (see Fig. 3.5) is not new and was first described by Parsons in 1904, advancing suggestions from a Royal Society committee. The great attraction is that all the energy requirements of most communities can be met by drilling to 5,000–7,000 metres deep; the problem is creating the interlinking system between wells with sufficient heat transfer area at these great depths. Since 1970, there has been approximately 35 years of work (representing several thousand man years of effort) and about $500 million spent worldwide in advancing this technology. An internal report from the European Commission has suggested that 15% of Europe’s power could come from this deep technology. Cornwall in the UK is one of the best potential locations in Northern Europe outside the volcanic regions. Parsons, when he described the basic process, said it would take 85 years before anybody took his ideas seriously—perhaps that time is arriving. There is also interest in using the HDR concept at shallower depths, purely for the production of heat, and several European countries have projects underway or actually in operation. An in depth review of this technology was recently presented at The Royal Society, (Tester et al., 2006)

Medium-temperature resources

41

Injection pump Makeup water

Power Plant Sediments and/or Volcanics

Injection well Production well

10,000-30,000 ft Depth

Low permeability crystalline Basement Rocks

3-10 km Depth

Figure 3.5 A hot dry rock (HDR) geothermal installation.

Another area of advanced work for the geothermal industry is the exploitation of supercritical resources. At some locations it is possible to access fluids at temperatures and pressures in the super critical regime (for water). These conditions have been identified in Japan and Italy and are now being exploited in Iceland (Fridleifsson and Elders, 2005). Provided that the borehole pressures and temperatures can be handled safely, the specific power output of this type of resource is considerably higher than conventional power production wells.

Medium-temperature resources More than 70 countries have installations taking hot water directly from the ground at 40◦ C to 150◦ C, over three times the number with high-temperature applications. The top four countries in terms of direct use, China, United States, Iceland, and Turkey, account for 68% of the geothermal energy used directly as heat. As the required source temperature diminishes, so the geographic constraints relax. For example, even in the UK (BGS, 1986) there is one famous

42 Geothermal energy

geothermal spa complex at Bath, and one geothermally fed district heating system at Southampton. There is potential for a few more locations; but the economics are generally unattractive at current gas prices (Batchelor et al., 2005). Fig. 3.6 shows the distribution of types of direct uses without heat pumps; worldwide,

Aquaculture 6% Process Heat 6% Greenhouses 11%

Other 4%

Bathing/swimming 43%

Space heating 30% Figure 3.6 Natural uses of geothermal energy worldwide (without heat pumps).

Figure 3.7 Two wells in Hungary supplying heating water to a housing complex.

Low-temperature systems with heat pumps

43

these applications utilize approximately 48,700 GWh (thermal), saving at least 10 million tonnes of carbon dioxide per year compared to burning gas. Fig. 3.7 shows an example of a direct use application in Hungary—in this case two wells supply medium temperature geothermal water to a housing complex. For a detailed assessment of direct use utilization the reader is referred to the recently published worldwide review undertaken following the 2005 World Geothermal Congress (Lund, Freeston, and Boyd, 2005).

Geothermal energy as a sideline of oil and gas industries Whereas deliberate efforts to extract geothermal energy often present challenges for commercial development, the oil and gas industries achieve this as a sideline. One major oil company has recently been involved in evaluating the feasibility of using the associated production of water, at moderate temperature, to offset power requirements for processing. Technically it appears feasible; a US university study has also looked at the utilization of produced water (Mckenna and Blackwell, 2005). Currently, the key contribution that the oil and gas business makes to geothermal energy is exploration. The oil companies, of course, are less than delighted when they encounter large quantities of hot water! The HDR site at Soultz in France was discovered by drilling beneath an oil field (Pechelbron) into a large hot water resource. Work is underway to investigate the use of the higher temperature produced fluids from oil and gas operations, with a UK designed, high-efficiency binary expander (Stosic et al., 2003) to generate electricity locally for certain oil and gas production facilities. This same expander appears to offer the opportunity for significant growth in power generation from medium temperature resources.

Low-temperature systems with heat pumps As the requirements for specific ground temperatures for particular applications are relaxed, the areas suitable for viable geothermal utilization expand rapidly. The two previous categories of resources are generally associated with large, semicentralized systems because of the need to use deep, capital-intensive boreholes in order to reach high enough temperatures. By contrast, low ground-temperature systems used with heat pumps are suitable for small scale, even domestic, systems and can be used anywhere to heat, to cool, and to provide domestic hot water. The technology is not new; it has roots back to William Thomson, (Lord Kelvin) in 1852 and work by a Royal Society committee (Royal Society, 1869). Worldwide, the installed base of geothermal heat pumps now exceeds 15,750 MWt , a sevenfold increase of capacity in 10 years; almost all these

44 Geothermal energy

installations are in North America and Europe, estimated as 1.3 million 12 kWt equivalent units (thought to be about two million actual installations, Systemes Solaires, 2005). Geothermal heat pumps are saving over four million tons of carbon dioxide a year (provided they displace gas as the heating fuel). The geothermal sources are either open-loop systems using the ground water directly through an evaporator heat exchanger, or closed-loop systems using a water based antifreeze mixture circulating through sealed pipework in boreholes or trenches. One variant on open-loop systems that is becoming attractive is the use of abandoned mines to form the subsurface ‘heat exchanger’. An entire conference has recently been devoted to this potential energy resource (see Malolepszy, 2001). For example, in the UK, large projects are being considered for the former Monktonhall Colliery in Scotland and in the Camborne and Pool Urban Regeneration area of Cornwall using abandoned tin and copper mines clustered around the old Dolcoath Mine, once the deepest and hottest mine in the world. Closed-loop installations allow the technology to be used anywhere; for example, in Europe they range from the smallest housing unit using a 4 kWt heat pump to a 9,000 kWt heating system in Norway. Switzerland has the highest density of units at over 1 system per 2 km2 and more than 30,000 operating systems, with 3,000 units per year being installed. In contrast, the UK has about 550 systems (early 2005) with some 100 new systems under construction in early 2005. Development of reliable heat pumps and the availability of high density polyethylene pipework have been key factors in making the technology applicable in a wide variety of situations. A general lack of understanding of the effective use of the systems by architects, building services engineers, and main contractors is perceived as a significant impediment to current growth. The reader is referred to the chapter by Dell and Egger (Chapter 12) for an analysis of the possibilities which have been implemented in Austria. A typical European 6 kWt system on a newly built, 100 m2 house will use less than 3,500 kWh of electricity for the heat pump and circulation system to provide about 13,000 kWt h to heat the house and domestic hot water. For one house, this will save 1.5 tonnes of carbon dioxide compared to gas and 3.6 tonnes compared to oil each year (based on UK figures). An added advantage of these systems is that they can incorporate reversible heat pumps to provide cooling at very little additional cost. An up to date worldwide assessment of geothermal heat pumps is provided by Lund, Freeston and Boyd (2005), with a discussion of worldwide application of the technology summarized in a paper for the 2005 World Geothermal Congress (Curtis et al., 2005).

Potential for future growth

45

Potential for future growth Low-temperature systems with heat pumps will have the biggest impact in the near future on the growth of utilization of geothermal energy. The growth is unlimited: there is no reason why every new building with a normal load profile would not benefit from such systems. Some new buildings are not suitable for geothermal energy, for example those with loads that peak over short intervals, but have otherwise low occupancy, for example religious meeting facilities. A limitation on the rate of growth for all other forms of geothermal system is the requirement for pre-feasibility studies to determine ‘is it hot enough?’, ‘can it flow at a high enough rate?’ and ‘is there enough of it?’. Even groundsource heat-pump systems need to be capable of being dug and drilled without undue cost; fortunately only very few sites present insuperable problems. This exploration phase or ‘geological risk’ assessment prior to establishing a major project is usually funded by national or supra-national organizations. There is a steady flow of long-term power generation projects developing in East Africa, South East Asia and Central/South America that will eventually support over 29,000 MWe of future systems in these areas (Stefansson, 1998). Two main studies have examined future growth prospects. The first study which looked at ‘proven resources’ and existing markets (Reed et al., 1999) concluded that a ten-fold expansion, i.e. a 100 GWe increase in power production, was feasible. The second report, by Stefansson, has looked further at undiscovered resources and the ultimate size of high-temperature systems (Stefansson, 2000). The analyses show that worldwide geothermal use could increase by a factor of more than 100, limited only by the impact of energy prices and environmental considerations. When the original paper was written, oil was trading at $10–20 per barrel and the USA was rejecting the concept of significant carbon emission reduction; only 0.2% of Stefansson’s total resource is in current use for power generation. For direct use Stefansson has estimated that the potential useable resources could provide 392,000 TWh/year, or more than three times the annual energy consumption today. The essential point is that the availability of the resource is not the limiting constraint. There seems to be no limit on the application of heat pumps other than the capability to provide awareness, installation, support, training, and design standards at the rate required for significant growth. Consider a situation with 50 MWe of firm renewable power from, say, hydropower or geothermal sources driving modern heat pump systems. Such a system would deliver up to 200 MWt of renewable energy at the points of use with much higher savings of emissions compared to those from the electricity component alone.

46 Geothermal energy

Conclusions Geothermal energy is one potential source of future energy supply that is already established and provides a significant fraction of the renewable energy worldwide. It has the potential for further substantial growth, making a large contribution to the reduction of emissions, particularly in developing countries. The resource is available in one form or another in every country and can provide base load electricity and heat on a continuous and sustained basis. Universities are already delivering specialist training courses under a UN programme in Iceland, Italy, and New Zealand. Annual training and awareness programmes in direct use are provided through the very successful ‘Geothermal Days’ programme, supported by the International Geothermal Association. The geothermal community is doing its utmost to raise the profile and awareness of the technologies and to promote the consideration of geothermal energy at the earliest phases of a project. The future is very bright and secure for geothermal energy; the heat from the Earth will have a major role to play in the era ‘beyond oil’.

Acknowledgements Two main sources of data were used for the preparation of this chapter. They were the principal summaries for the International Geothermal Association, World Geothermal Congress 2005 held in Turkey; one paper covers Power Generation (Bertani WGC, 2005) and the other Direct Uses (Lund et al., WGC 2005). The geothermal community is quite small and many colleagues in GeoScience/EarthEnergy Ltd and in the International Geothermal Association have provided input. Particular assistance was provided by Peter Ledingham and John Garnish. The views expressed in this paper are entirely our own and are not necessarily endorsed by any organization.

Resources and further information Armstead, H. C. H. 1983. Geothermal Energy, E. & F. N. Spon, London. British Geological Survey, 1986; Geothermal Energy-the potential in the United Kingdom, Downing, R. and Gray, D. (eds), Her Majesty’s Stationery Office. Barbier, E. 1997. Nature and technology of geothermal energy: a review. Renewable and Sustainable Energy Reviews, 1, 1/2, 1–69. Batchelor, A., Curtis, R., and Ledingham, P. 2005. Country update for the United Kingdom, International Geothermal Association, World Geothermal Congress 2005, Turkey. Bertani, R. 2005. World wide geothermal generation 2000–2005: state of the art, International Geothermal Association, World Geothermal Congress 2005, Turkey.

Resources and further information

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Bertani, R. 2005 World geothermal power generation in the period 2001–2005, Geothermics, 34, 6, 651–90. Curtis, R., Lund, J., Sanner, B., Rybach, L., and Hellstrom, G. 2005. Ground source heat pumps—geothermal energy for anyone, anywhere: current worldwide activity, International Geothermal Association, World Geothermal Congress 2005, Turkey. Dickson, M. H. and Fanelli, M. 2005. Geothermal Energy: Utilization and Technology, Earthscan, London. DiPippo, R. 2005. Geothermal PowerPlants: Principles, Applications and Case Studies, Elsevier, London. Fridleifsson, G. O. and Elders, W. A. 2005. The Iceland deep drilling project: a search for deep un-conventional geothermal resources. Geothermics, 34, 3. International Geothermal Association, 2000, Plenary Session III, World Geothermal Congress 2000, Kyushu-Tohoku, Japan. Lund, J., Freeston, D., and Boyd, T. 2005. World wide direct uses of geothermal energy 2005, International GeothermalAssociation, World Geothermal Congress 2005, Turkey. Lund, J., Freeston D. H., and Boyd, T. L. 2005. Direct application of geothermal energy: 2005 worldwide review, Geothermics, 34, 6, 691–727. Malolepszy, Z. (ed), 2001; Geothermal Energy in Underground Mines Conference Proceedings , University of Silesia, Nov 21–23, 2001, Ustron, Poland. Mckenna, J. and Blackwell, D. 2005, Geothermal electric power possible from midcontinent and gulf coast hydrocarbon fields, Oil & Gas Journal, forthcoming. Parsons, 1904, President’s Address to the Engineering Section, British Association for the Advancement of Science, Transactions of section G, BAAS Report, 667–76. Reed, M., Galwell, K., and Wright, M. 1999. The Potential for Clean Power from the Earth, Geothermal Energy Association, USA. REN21. 2005. Renewables 2005, Global Status Report, REN21 Renewable Energy Policy Network, Worldwatch Institute, Washington DC. Royal Society, 1869; Report of the Committee for the Purpose of Investigating the Rate of Increase in Underground Temperature. BAAS Report, Compiled by J. D. Everett, pp. 176–189. Sigfusson, A. 2003. Iceland: pioneering the hydrogen economy, Foreign Service Journal, December, 62–5. Stefansson, V. 1998. Estimate of the world geothermal potential, Geothermal Training Programme, 20th Annual Workshop, Orkustofun, Reykjavik, Iceland. Stefansson, V. 2000. Competitive status of geothermal energy in the 21st century, World Geothermal Congress. Stosic, N., Kovacevic, A., and Smith, I. 2003. Opportunities for innovation with screw compressors, Proc I Mech E, Journal of Process Mechanical Engineering, 217, 157–70. Systemes Solaires, 2005. EU and worldwide geothermal energy inventory, Systemes Solaires No 170, Barometre Geothermie. Tester, J. W. 2006, Assessment of the Energy Supply Potential of Engineered Geothermal Systems (EGS)–The Royal Society Discussion Meeting on ‘Energy…for the Future’, London 2006.

48 Geothermal energy

Web Resources Dickson, M. H. and Fanelli, M. 2004. What is Geothermal Energy?, Istituto di Geoscienze e Georisorse, CNR , Pisa, Italy. http://iga.igg.cnr.it/geo/geoenergy.php International Geothermal Association: http://www.iga.igg.cnr.it/index.php Geothermal Resources Council: http://www.geothermal.org/index.html World Geothermal Congress http://www.wgc2005.org Geothermal Energy Association: http://wwwgeo-energy.org European Geothermal Energy Council: http://www.geothermie.de/egec_geothermal/ menu/frameset.htm Geothermal Heat Pump Consortium: http://www.geoexchange.org International Ground Source Heat Pump Association: http://wwwigshpa.okstate.edu Geo-Heat Center: http://geoheat.oit.edu

The authors Dr. Tony Batchelor is the Chairman and Managing Director of GeoScience and EarthEnergy Ltd, based in Falmouth. Tony was appointed Managing Director of GeoScience in 1985, with the objective of developing a centre of excellence in skills to support both geothermal engineering and allied work in fields such as oil and gas drilling. He is regularly invited to speak at national and international conferences and as served as Director of the International Geothermal Association; and is the author or co-author of more than sixty papers and three books. Dr. Robin Curtis is the Technical Manager of EarthEnergy Ltd—part of the GeoScience group. Robin was trained as a nuclear engineer, and has worked on energy from the ground for the past 20 years. Since the early 1990s, he has been instrumental in bringing ground source, or geothermal, heat pumps into vogue in the UK microgeneration sector. As well as being responsible for the design and implementation of a wide range of UK installations, he has generated a number of publications, and has made numerous presentations on the subject.

4.

Wave and tidal power Dean L. Millar Introduction Wave energy resources Types of wave energy converters Pelamis Archimedes Wave Swing WaveDragon Energetech Powerbuoy Comparing wave energy converters—‘Wave Hub’ Tidal energy resources The nature of tidal energy resources Tidal barrage schemes Environmental impacts Tidal current turbines Turbine technologies under development Horizontal axis turbines SeaFlow and SeaGen 61 Vertical axis turbines Davis turbines 61 Gorlov Helical Turbine 62 Cyclodial Turbines 63 Hydrofoil Devices Stingray 63 SeaSnail 63 Venturi Devices Hydroventuri 63 Ranking of marine renewable energy technologies Assessment of wave and tidal current resources (UK) Summary and conclusions Resources and further information

50 50 51 53 54 55 55 55 55 56 56 57 59 59 60 60 61

63

63 64 64 67 69

50 Wave and tidal power

Introduction This chapter reviews how electricity can be generated from waves and tides. The UK is an excellent example, as the British Isles have rich wave and tidal resources. The technologies for converting wave power into electricity are easily categorized by location type. 1.

Shoreline schemes. Shoreline Wave Energy Converters (WECs) are installed permanently on shorelines, from where the electricity is easily transmitted and may even meet local demands. They operate most continuously in locations with a low tidal range. A disadvantage is that less power is available compared to nearshore resources because energy is lost as waves reach the shore.

2.

Nearshore schemes. Nearshore WECs are normally floating structures needing seafloor anchoring or inertial reaction points. The advantages over shoreline WECs are that the energy resource is much larger because nearshore WECs can access long-wavelength waves with greater swell, and the tidal range can be much larger. However, the electricity must be transmitted to the shore, thus raising costs.

3.

Offshore schemes. Offshore WECs are typically floating structures that usually rely on inertial reaction points. Tidal range effects are insignificant and there is full access to the incident wave energy resource. However, electricity transmission is even more costly.

Tidal power technologies fall into two fundamental categories: 1.

Barrage schemes. In locations with high tidal range a dam is constructed that creates a basin to impound large volumes of water. Water flows in and out of the basin on flood and ebb tides respectively, passing though high efficiency turbines or sluices or both. The power derives from the potential energy difference in water levels either side of the dam.

2.

Tidal current turbines. Tidal current turbines (also known as free flow turbines) harness the kinetic energy of water flowing in rivers, estuaries, and oceans. The physical principles are analogous to wind turbines, allowing for the very different density, viscosity, compressibility, and chemistry of water compared to air.

Wave energy resources Waves are caused by winds, which in the open ocean are often of gale force (speed >14 m/s). Wave energy resources are thus highest at latitudes between 30◦ and

Wave energy resources

51

30 40 60

70 40

40

40

20

30

20

15

20

20

10 10

20 20

30 50 70

20 20

20 40

30

30 50 40

20

20 30 60

30 70 100

Figure 4.1 World wave power density map (figures show kW/m of wave crest length) highlighting latitudes where resource is highest. Source: CRES, 2002.

60◦ , north or south, where ocean winds are strongest (Fig. 4.1). Maximum wave strength occurs when the rate of energy transferred from the wind matches the rate at which the wave loses energy from friction, surface current production, and ‘whitecapping’. Waves travel great distances in deep water with little energy loss, emerging from storm areas as smooth, regular waves known as ‘swell’. The height and length of waves in deep water thus depend on the speed of the wind, and its duration, which is longer for unobstructed expanses of sea (the fetch). Once reaching shallow water (depths less than half the wavelength) waves depend also on the nature of the seabed. Governments across many countries and regions have commissioned investigations into wave energy technology. In a study by the US Electric Power Research Institute (Previsic et al., 2004) four assessment criteria were used. 1.

Design maturity, covering: structural elements, power, mooring, survivability/failure, grid integration, performance, operation and maintenance, deployment, and recovery.

2.

Capital cost of purchase of a device.

3.

Company viability and willingness to licence the technology.

4.

Particular Site Advantage. Wave energy converters exploiting opportunities at specific sites that are not present elsewhere.

Types of wave energy converters Wave energy converters fall into several classes based on how they interact mechanically with waves. In all cases a reaction force is needed (power

52 Wave and tidal power

production requires relative motion) and this is provided either by inertia or by mooring to the seabed. Wave power plants are damaged by extreme weather, so they must be located or moored so as to minimize this happening. For maximum efficiency a WEC must remain ‘in phase’ with the wave motion. This is achieved with large dimensions and sophisticated motion control systems, each giving cost increases that must be justified by the greater power produced. Fig. 4.2 shows the different components of wave motion that can be exploited, and Fig. 4.3 shows the different principles of operation of WECs.

Wave direction

Heave Linear vertical motion Surge Linear horizontal motion Sway (plan view) Linear horizontal motion Wave crest

Roll Rotation about horizontal axis Pitch Rotation about horizontal axis (perpendicular to paper) Sway (plan view) Rotation about vertical axis (perpendicular to paper)

Figure 4.2 The different components of wave motion that can be exploited by wave energy converters.

Wave energy resources

Hydraulic fluid

Wave pitching,heaving and/or surging forces cause relative motion between absorber (a) and reaction point (b), which drives working fluid through pump( ) or turbine(∝)

Spine

Pitch

Duck 10

Buoy

Pitch and heave

Hydraulic fluid Plate 9

8

53

Yoke

Hydraulic fluid

Buoy

Raft

∝ Air

Buoy

3 Deadweight Seawater

Buoy

Buoy

Heave Seawater

7

6

Seawater 5

Air

Float Fixed platform

Plate

∝

2

Fixed platform

Deadweight Cylinder

Heave and surge

12

Tapered channel

Seawater Hydraulic fluid

Spine

Reservoir

Flap

Air

11

1

4

∝

Surge

∝

Piled anchors Flexible bag

Seawater

Fixed platform

A:

B:

Free surface

Rigid or flexible structure Inertial structure

Seafloor anchor

Fixed structure

Inertial or fixed structure

Figure 4.3 Classification of wave energy converters according to A: the way energy is absorbed, B: the type of reaction point. Source: Hagerman, 1995. See also, Falnes, 2003.

Pelamis The Pelamis, (see Fig. 4.4) developed by Ocean Power Delivery Ltd, UK, most closely resembles concept 9 in Fig. 4.3. The semi-submerged system is 150 m long, weighs 380 tonnes and comprises four 3.5 m diameter cylindrical sections linked by 3 articulating joints. Each joint has a 250 kW rated power module. As waves propagate along the length of the device, the articulating joints actuate hydraulic rams that pump fluid to a smoothing accumulator and on through

54 Wave and tidal power

a hydraulic motor. The hydraulic motor drives a generator to produce electricity. The reaction point for the Pelamis is successive wave crests. The unit is designed to be slack moored in water depths of 50 to 100 m. Archimedes Wave Swing The sea-bed-anchored Archimedes Wave Swing (AWS) (type 6 in Fig. 4.3, see also Fig. 4.4) comprises two submerged, floating cylindrical shells, one mounted inside the other (http://www.waveswing.com). As a wave moves through, the outer cylindrical shell moves up and down with respect to the static inner cylinder on a cushion of pressurized trapped air, producing electricity from the motion via a linear generator. A 2 MW rated AWS was deployed off the Portuguese coast in 2004 and connected to the electricity grid. For tests, the 6 m diameter half-scale prototype was mounted on a static seabed platform. The added mass of the platform produced a total displacement of 7000 tonnes. Rather than a submersible pontoon, commercial devices will utilize a single mooring to anchor the inner cylinder. Thus they will be far less massive.

Group 1 – Development near completion and full-scale long-term testing in the ocean underway Ocean power delivery—Pelamis

Group 2 – Development near completion, only deployment,recovery and mooring issues are yet to be validated. Construction of full-scale devices is in some cases completed. Energetech

Wave dragon

Teamwork technology Ltd – Wave swing

Figure 4.4 Examples of wave energy converters in operation or under test, classified according to the US EPRI (Previsic et al., 2004).

Comparing wave energy converters—‘Wave Hub’

55

WaveDragon The WaveDragon (see Fig. 4.4) is a sea-bed-anchored, floating WEC that resembles types 1 and 12 of Fig. 4.3 (WaveDragon ApS, 2006). Its parabolic shaped collecting arms face the oncoming wave fronts and focus and channel the waves toward a central ramp, causing the water to enter a reservoir behind it. The water level in the reservoir is thus maintained above the still water level of the open sea. The small head is used to drive water through turbines to produce electricity. Energetech The nearshore/shoreline WEC developed by Energetech (see Fig. 4.4) is based on an oscillating water column power take off unit that is located at the focus of a parabolic shaped wave reflector. Entering waves cause the water level to rise rapidly up a confining column, driving air through a turbine. As the water level falls when the wave retreats, air is sucked back through the turbine also producing power on this intake stroke. The parabolic wave reflector amplifies the height of the waves arriving at the column inlet. The complete unit is sea-bed-mounted on a fixed platform, and represented by device 2 in Fig. 4.3. Energetech prototype units are built from steel, and are 36 m long and 35 m wide with a mass of 485 tonnes. To maximize energy capture they employ a sophisticated control system with a pressure sensor located ahead of the device to tune the device to the period of incident wave phases (Alcorn et al., 2005; also http://www.pontediarchimede.com). Powerbuoy The Powerbuoy, developed by Ocean Power Technologies (OPT) corresponds most closely to device 5 or 6 in Fig. 4.3. It has an outer cylindrical float that rises and falls under the propagating wave. The power take-off equipment is housed at the bottom of an inner cylinder that maintains reference using anchoring chain and heave reaction plates. The device maximizes energy capture using a ‘smart’ control system. The first Powerbuoy prototype was deployed off Atlantic City, New Jersey in 1997, and has evolved through various changes. OPT now has several active projects underway in Hawaii, New Jersey, Spain, France, and the UK (Discovery Channel, 2005).

Comparing wave energy converters—‘Wave Hub’ Performances of WECs can be compared both technically and commercially. In absolute terms, WaveDragons have the highest rated capacity, followed by the AWS, then Pelamis. However, when comparing the efficacy of devices their

56 Wave and tidal power

relative scales and fabrication costs need to be taken into account. A good measure of relative efficacy is the annual electrical energy produced divided by device capital cost. When the latter is unavailable, it is possible to use the mass of the device as an analogue for capital cost. Such measures may rank the Pelamis device above the others mentioned, despite it having the lowest rating. It is necessary to test WEC devices in real situations, involving multiple units operating in array configurations connected to the grid. Choice of a particular WEC depends on how its characteristics are suited to the site resource and how straightforward it is to deploy, moor, recover, and maintain large numbers of identical devices in what are often challenging conditions. Wave Hub is a development facility for testing marine energy systems. It occupies a 4 km × 2 km area off the north coast of Cornwall, UK, and provides facilities for wave power project developers and WEC device developers to assess the operational performance of arrays of WEC units. The Wave Hub project helps avoid the need for device developers to commit capital for grid connections and planning permission for each WEC technology separately. Also, WEC projects can be financed without too large a ‘lone horse’ financial risk that might otherwise deter investors. Wave Hub allows comparisons between WEC technologies operating side-by-side in the same resource to determine which technology utilizes the resource most efficiently. Although the global wave energy resource is sufficient to satisfy the world’s electricity consumption twice over, exploitable resource sites are relatively scarce at present. Escalation of wave power technology will depend on prioritizing technologies that utilize resources most efficiently and cost effectively.

Tidal energy resources The nature of tidal energy resources Tides result from the cyclical nature of the gravitational attraction between the mass of seawater on the Earth’s surface and the mass of the Sun and the Moon. We experience tides mainly at shorelines, but even in the absence of land, tides would represent a ∼0.4 m bulge in sea level that circles the globe once every 24 hours and 50 minutes. Tides are therefore akin to waves with a 12.4 hour period: as they approach a shoreline, the reduced water depth causes shoaling, and their height and speed are enhanced as they travel up narrowing estuaries. Headlands and peninsulas can also lead to enhanced tidal current velocities as water is swept around from one tidal basin to another. The world’s highest tidal range occurs at the Bay of Fundy, Nova Scotia, Canada (∼18 metres). The predominant type of tide around the world is called semi-diurnal. Locations with semi-diurnal tides have two high-water times and two low-water times per day. Diurnal tide locations have one high-water time and one low-water time each day. Mixed tidal locations

Tidal barrage schemes

57

experience one tidal cycle with high tidal range and one tidal cycle with low tidal range each day. Energy recoverable from tidal resources is variable, intermittent, but predictable; the latter characteristic offering an advantage of tidal energy over other forms of renewable energy, with the exception of geothermal energy. The predictable variability arises over various time scales. First and most obviously, the available energy varies over a cycle of approximately 14 days between spring tide and neap tide ranges. Second, the annual energy yield can vary up to 8% from year to year; due to natural variations of the orbital trajectories of celestial bodies driving tides. Third, the recoverable power from a tidal resource varies appreciably within an individual tidal cycle and there will be some occasion during the tidal cycle of 12 hours, 25 minutes—where the output power will fall to zero—and another moment when the output power will peak. These variabilities, although predictable, will not correspond with periodic power demands, and this imposes important constraints on the design of tidal power plants which must incorporate systems for storing the energy or buffering (smoothing out) its magnitude. In addition, tidal height is affected by local weather conditions such as strong winds, which can act with spring tides to produce a tidal surge. As high-tide times vary along coastlines, one solution is to employ a number of smaller tidal power plants along a coast so that the peak and zero output of each device is staggered in time. This gives, collectively, a more continuous output, albeit with higher costs. This strategy is unavailable to large, barrage-type tidal power plants, but output power can be smoothed by employing multiple adjacent impounded basins. Water flows from one basin to another (and thus output power is maintained) at times in the tidal cycle where a single basin scheme would have zero output power. Double and triple basin barrage schemes are very attractive in this respect and can even overcome some environmental concerns about habitat loss. Multiple basin schemes have the additional benefit of much lower peak output as well as much more continuous operation. Cost-wise, this means that the specifications for switch gear, transformers, and transmission cables are lowered, helping to offset the higher capital requirements for dam construction in comparison to single basin schemes.

Tidal barrage schemes Tidal barrage schemes impounding huge volumes of water by means of dams, sluices, and locks historically have attracted the most investment attention to date, but this is changing. Like large hydroelectric dams, they introduce significant environmental issues that hinder their development (Kerr, 2005). Table 4.1 lists the world tidal energy resources that are technically accessible for barrage

58 Wave and tidal power Table 4.1 Locations suitable for large scale barrage projects. Country

Region

British Isles France USA

Severn/Irish Sea Normandy/Brittany Alaska

Canada Argentina Argentina Russian Fed. India Australia China Korea Russian Fed. Russian Fed.

Bay of Fundy Golfo San Matias Bahia Grande Beloye More Gulf of Khambhat Bonteparte Archipelago Formosa Strait/Hangzhou Wan Korea Bay/Yellow Sea Sakhalinskiy Zaliv Penzhinskaya Guba/Zaliv Shelikov

Mean tidal range (metres)

Approx resource at ‘reasonable cost’ (GW)

8 7 7

18 15 5

10 5 7 5 6 6 5 5 5 5

20 80 20 12 8 5 10 1 10 30

Tide Type

Semi-diurnal Semi-diurnal Semi-diurnal Mixed Semi-diurnal Semi-diurnal Semi-diurnal Semi-diurnal Semi-diurnal Semi-diurnal Semi-diurnal Semi-diurnal Diurnal Diurnal

Sources: Boyle, 2003; Pidwirny, 2005.

projects. The total world installed capacity for tidal power is around 234 GW, and if fully exploited this is estimated to provide 512 TWh/year. The world’s largest operational tidal barrage scheme is the Barrage-de-la-Rance in Brittany, France (mean tidal range: 8.55 m) with an installed capacity of 240 MW. Since 1967, the structure has provided a four-lane, 750 metre-long highway between the towns of St Malo and Dinard. It houses 24 pump-turbine units, sluice gates and lock arrangements for light marine craft, and generates electricity during both ebb and flood tides. The scheme impounds a basin of 22 km2 and produces 0.64 TWh/annum. The next largest system, rated at 20 MW with output 50 GWh/annum, impounds a 15 km2 basin atAnnapolis Royal, Nova Scotia, Canada where the mean tidal range is 6.4 m. Other schemes in operation are in China and Russia. Total installed tidal barrage generating capacity for China is estimated at 5.7 MW, the main plant being the Jiangxia Tidal Power Station in Leqing Bay (tidal range: 5.1 m, 3.9 MW, 5 GWh/annum). In Russia, the 400 kW Kisalaya Guba power plant is located north of Murmansk in a gulf opening to the Barents Sea. Although the number of tidal barrage schemes actually operational and feeding electricity into a grid are still few in number, there is great activity in feasibility studies and project proposals. The range is huge, with the largest being a 87.4 GW proposal that would impound a sea area of 20,500 km2 in Penzhinskaya Bay, Siberia.

Tidal current turbines

59

Environmental impacts The La Rance scheme was completed in 1967. During its construction the river was isolated from the sea for approximately 3 years, and this led to the death of many species of plants and animals that had previously flourished in estuarine and mudflat environments. Populations started to recover once the connection with the sea was re-established, and more so when the barrage started operations although modifications were needed to alleviate silting. The barrage also exacerbated the problem of algal blooms caused by nitrate based fertilisers. Prior to construction of the barrage, La Rance was an important route for the transport of goods inland from the port of St Malo. Towns along the river and canal systems that depended on this trade have had to adapt and goods that were originally transported along the river are now displaced to the roads. Despite these negative aspects, a tour of the La Rance basin today reveals a very attractive environment that appeals to tourists and regular leisure water users. Habitats and floral and faunal populations have recovered. A study of the environmental impacts of a tidal barrage power station constructed across the Severn Estuary (UK), concluded that a barrage may actually be beneficial because it reduces the speed of tidal currents on the river/sea bed to a level at which it can be colonized by species currently unable to obtain an anchoring (Kirby and Shaw, 2005). Some studies, for example by Dadswell and Rulifson, 1994, suggest that fish and other marine animals may be detrimentally affected by turbine motion in barrage schemes. The general consensus is to examine alternative methods of harnessing tidal energy. Thus tidal current turbine technology that operates in the free stream of tidal flows without the need for impounding dams has attracted significant interest and investment in recent years.

Tidal current turbines In contrast to barrage projects which harness the potential energy of a large head of water, tidal current turbines harness the kinetic energy of freely flowing water. The kinetic energy resource is similar in magnitude to the potential energy resource harnessed in a tidal barrage scheme. The locations where enhanced concentrations of kinetic energy are available broadly coincide with identified locations for barrage projects. However, tidal flow round coastline obstructions, such as headlands and peninsulas, enhance current speed and provide locations where tidal current turbine technologies can be exploited whereas tidal barrage technology cannot. The threshold peak tidal current velocity for an exploitable resource is about 1.5 m/s. The largest rating of a tidal current turbine currently being considered is 1 MW, rather less than that of the two largest operating barrage schemes. A large increase in scale is thus required: for example, had tidal current turbines been installed in

60 Wave and tidal power

La Rance estuary, 240 of the largest units would have to be installed to reach the same installed capacity and similar annual electrical power yield. There are several advantages of tidal current turbine developments over tidal barrage projects. 1. As more turbine units are required, there are greater opportunities for economies of scale in turbine manufacturing and lowered capital costs than with tidal barrage systems. 2. Tidal current turbines are more flexible in respect of the locations where they can be deployed. 3. Tidal current turbine farms do not require water-impounding structures and are thus less restricted by environmental impact problems. 4.

Removing the requirement for dam construction means that tidal current turbine developments can be smaller and less capital intensive (but not necessarily cheaper, in terms of £/kW installed capacity).

The physics of tidal current turbine technology is similar to that for wind turbines, except that the density and viscosity of water are much higher than air. Because of this similarity, and because institutional investors understand and are already convinced about wind power developments, there is a close financial and commercial development analogue for developers of tidal current turbines. Turbine technologies under development Classification of conventional tidal current turbines types closely mirrors those for wind turbines. The main distinction is whether the rotor axis of the turbine is mounted horizontally or vertically. Alternatively, the energy in tidal currents can be extracted by hydroplanes or harnessed indirectly, by devices (venturi) that convert water flow into air flow, which is then used to drive the generator. Horizontal axis turbines The choice of rotor size, and hence the power rating, depends primarily on the depth of water in which the turbine is to be deployed (Bryden et al., 1998). Provided shipping can be excluded from the vicinity of the turbine installation then the rotor axis depth and the rotor diameter can be half the lowest depth of water at low tide. The world’s first grid-connected horizontal axis tidal current turbine was installed in Norway in 2003 to supply Hammerfest, the world’s most northerly

Tidal current turbines

61

town. The 300 kW rated turbine has a 22 m diameter three-blade rotor and is mounted on a 120 tonne steel tripod structure that rests on the bed of the Kvalsundet strait and is stabilized by additional weights totalling 200 tonnes. The 54 tonne nascelle contains the generator, gearbox, drive train, and control components, including a pitch regulating mechanism that allows the unit to harness reversing tidal currents. Within the strait, which is 400 m wide at its narrowest point and 50 m deep, the average tidal current velocity is 1.8 m/s (peak of 2.5 m/s) and each unit can provide 0.7 GWh of electricity per year. SeaFlow and SeaGen SeaFlow is a prototype horizontal axis tidal current turbine that has an 11 m diameter, two-blade rotor with variable pitch. It is rated at 300 kW, attainable when the tidal current is 2.7 m/s or greater. The rotor, drive train, and generator are mounted on a chassis that can be raised out of the water to allow inspection and maintenance without recourse to dive teams. The chassis travels up and down a vertical steel pile drilled into the seabed. The prototype was designed to consider only a single tidal current direction in testing. The power produced in tests has been reported to be 27% greater than predicted, and this success has increased confidence in tidal current turbine technology and secured further funding from the UK government for the developers, Marine Current Turbines Ltd. The next stage is a device called SeaGen which has twin rotors, each rated at 500 kW, which operate when the tide flows in either direction. A turbine farm comprised of multiple 1 MW SeaGen units is under consideration, as depicted in Fig. 4.5. The rating per unit is unlikely to increase much above 1 MW: SeaGen deployment depths are limited to 40 m, so that the rotor size cannot be greater than 20 m in areas where marine traffic will be excluded, and around 15 m where marine traffic will retain access. A project with 133 MW capacity would comprise 133 SeaGen units, spaced 60 m apart to form a linear array 8 km long, and could provide an output of 466 GWh/annum. Vertical axis turbines One important advantage of vertical axis tidal current turbines is that they require no blade pitch control to allow for reversing of the tidal current direction; the rotor rotates the same way irrespective of the direction of the impinging fluid. Davis turbines In the free stream Davis hydroturbine, developed since 1981 by Blue Energy Inc. of Canada, the axis of rotation is vertical and the rotor comprises 3 or 4 vertical, straight hydrofoil-profile blades mounted on radial arms along the length of the runner. Davis turbines operate in either ducted or unducted conditions as stand-alone units or as units in a ‘tidal fence’. In many cases, the gearbox and generator can be located on top of the rotor, out of the water, which simplifies routine maintenance. To date, six prototypes have been

62 Wave and tidal power

Figure 4.5 Artist’s impression of a tidal current turbine farm using horizontal axis turbines (Source: www.marineturbines.com).

tested, ranging from small laboratory scale test units to a 20 kW unit connected to the Niagra Power Corporation grid in 1983 and a 100 kW unit connected to the Nova Scotia Power Corporation grid in 1984 (Takenouchi et al., 2006). Blue Energy Inc. of Canada have been involved with various tidal energy development projects, including a 500 kW demonstration plant of floating Davis turbine units off British Columbia, Canada and a 4 km long, 274 turbine, 2200 MW rating tidal fence concept that would cross the Strait of San Bernardino in the Philippines. Gorlov Helical Turbine The Gorlov turbine (Gorlov, 2001; Gorban et al., 2001) is a cross flow turbine with helical blades that run around a cylindrical surface with each blade having a hydrofoil profile. It shares the key advantage of the Davis turbine over many of the horizontal axis turbine units that, due to its axial symmetry, there is no need for blade pitch control. However, vertical axis hydro turbine units can become unstable at high speed, requiring shut down when the resource is highest. This problem can be overcome in Gorlov turbines because the helical blade geometry produces more stable running. Gorlov turbines feature in a large 90 MW project planned in Korea: a tidal fence development bridging the Uldolmok Strait between the Korean mainland and Jindo Island where peak tidal currents are 6.5 m/s.

Tidal current turbines

63

Cyclodial Turbines The Kobold turbine is a three bladed vertical axis device produced by Enermar. The pitch of the blades is variable and automatically regulated though means of the acting centrifugal forces and an asymmetrical blade profile. The rotor transmits power through a very high ratio (1:160) gearbox to a permanent magnet generator. The Enermar system is being applied in the Strait of Jintang (Zhoushan Archipelago) in China. Hydrofoil Devices Stingray The Stingray (http://www.engb.com/) uses a variable pitch hydroplane to extract energy from tidal currents. The hydroplane is attached to a support arm that rises and falls according to the sense of the hydroplane lift. This produces a ‘pumping’ motion to actuate hydraulic cylinders that pressurize oil and turn a hydraulic motor that runs the generator. The pitch of the hydroplane is adjusted continuously through each stroke of the supporting arm such that at the top of its stroke, the lift force acts downward. At the bottom of its stroke, the hydroplane pitch is again adjusted so that the lift force acts upward. SeaSnail The SeaSnail is designed primarily as a seabed platform for tidal current turbine devices. The platform is an evolution of the Stingray device in that it uses hydroplanes to create down-force to ‘pin’ the platform structure to the seabed. The enhanced down-force creates a greater resistance to shear loads that are primarily introduced as reaction thrusts from the energy capture components. The device is 15 m long by 12 m wide and has a mass of 30 tonnes. The six hydroplanes mounted on the chassis create a force equivalent to 200 tonnes. Although the SeaSnail prototype features a simple horizontal axis tidal current turbine for demonstration purposes, it is a move away from simply relying on steel or concrete mass to anchor seabed mounted structures, and will allow such marine energy capture units to be fabricated more cheaply. Venturi Devices Hydroventuri A device from Hydroventuri Ltd utilizes the static pressure drop occurring at the throat of a venturi-shaped duct which draws in air as water flows through. This air passes through a turbine, the shaft of which is connected to a generator. The advantage over other tidal current turbines is that the submergible components have no moving parts; the turbine and generator do not need to be mounted on a surface platform. The disadvantage is that a connection to atmospheric air to the submerged components needs to be maintained.

64 Wave and tidal power Table 4.2 Ranking of wave and tidal devices based on estimates of their G-value (annual yield /capital cost ratio). Device

annual kWh/tonne device mass)

(1) SeaGen (2) SeaFlow (3) Stingray on SeaSnail (4) Pelamis (WEC) (5) Rotech 1.5 (6) Stingray (7) Powerbuoy (WEC) (8) Archimedes WaveSwing (WEC) (9) WaveDragon (WEC)

9281 8002 6488 4034 3694 2884 2061 1184 521

Ranking of marine renewable energy technologies Wave and tidal current devices can be ranked on the basis of their G-values, the ratio of the annual yield to the mass of the device (mass being an analogue for capital cost). An example of such a ranking is given in Table 4.2. Despite its simplicity (the ranking assumes that cost relates directly to mass, and there are uncertainties in estimating the mass of some of the devices) it allows comparisons across many power conversion concepts and different forms of marine renewable energy. Current competition is strong for marine renewables, driven by commercial interests. Ultimately, four key factors will establish the system of choice for exploiting marine energy resources: • Accessibility of the resource. •

Simplicity of power conversion concept—the WaveDragon is easily the best in this respect.

•

Ease of operations and maintenance—devices running without diver intervention are best.

•

Proven survivability and efficacy of mooring arrangements—devices that break free from moorings and cause serious marine accidents may be banned from the sea.

Assessment of wave and tidal current resources (UK) Based on the Wave Hub model, the criteria for suitable sites for wave farms are easily identifiable: • Average annual wave power density >25 kW/m. •

Water depth of 50–60 m.

Assessment of wave and tidal current resources (UK)

65

•

Proximity of electricity distribution network with available capacity.

•

Outside major shipping routes.

•

Wave energy arrives at the site predominantly from one direction.

•

Proximity to onshore facilities to support operations and maintenance activities.

The site criteria for tidal turbine farms (based on SeaGen) are likewise summarized as follows: •

Peak current velocity on mean spring tide 2.5–3.0 m/s, in a normal current shear location.

•

Water depth 30–35 metres at Lowest Astronomical Tide (LAT).

•

Proximity of electricity distribution network with available capacity.

•

Outside major shipping routes.

•

Predominantly bi-directional tidal current directions—narrow tide ellipses.

•

Relatively low ratio of peak spring current speeds to peak neap current speeds.

•

Proximity to onshore facilities to support operations and maintenance activities.

Figs. 4.6 and 4.7 illustrate criteria applicable to the respective technologies and an estimate of sites allowing either a Wave Hub wave farm model or a large scale tidal current turbine farm to be considered. The numbers of sites identified against each model are summarized in Table 4.3. The tidal current resource is clearly the more significant both in terms of installed capacity and annual output. The reasons for this are threefold: there are more resource areas, the installed capacity per farm is over 100 MW higher, and the capacity factors of the devices are higher. The simplistic analysis illustrates a crucial factor restricting growth of either sector—access to an electricity transmission network. For the Hebridean and Orkney Islands, where both tidal current and wave power opportunities are appreciable, development of either type would justify extending the grid. This accessibility has been noticed by developers and regional public sector organizations and led to the Wave Hub project in Cornwall and the proposed WaveDragon deployment off Milford Haven. These regions have the resource and grid capacity to support one more development each. However, beyond this, the wave sector at least may find it very difficult to locate suitable development sites without major transmission and distribution network upgrades.

66 Wave and tidal power

400 kV 275 kV Mean Wave Power (kW/m of wave crest) >70 66 - 70 61 - 65 56 - 60 51 - 55 46 - 50 41 - 45

36 - 40 31 - 35 26 - 30 21 - 25 16 - 20 11 - 15 6 - 10 0-5

Land UK Continential Shelf & Channel Island Territorial Sea Limit

> 50m deep > 50m deep

50m deep

Figure 4.6 Wave energy resource assessment coverages of the UK. Upper left: UK electricity transmission grid. Upper right: Mean wave power density. Lower left: Boundaries of outer shaded areas identify the 50 m water depth contour. Lower right: Sites identified as suitable for wave power developments. Source for all base maps: ABPMer et al., 2004.

The situation is less severe for tidal current turbine developments because the north Somerset/north Devon, south Wales and Hampshire/Dorset coasts are well served with grid infrastructure where the resource is at its highest.

Summary and conclusions

67

Peak Flow - (m/s) > 4.01 3.51 - 4.00 3.01 - 3.50 2.51 - 3.00 2.01 - 2.50 1.75 - 2.00 1.51 - 1.75 1.25 - 1.50 1.01 - 1.25 0.76 - 1.00 0.51 - 0.75 0.26 - 0.50 0.11 - 0.25 < 0.10

Land UK Continental Shelf & Channel Island Territorial Sea Limit

400 kV 275 kV

Sites considered by Black & Veatch, 2004 Other sites considered by MCT Ltd

> 40 m deep

< 40 m deep

> 40 m deep

Figure 4.7 Tidal current resource assessment coverages of the UK. Upper left: UK electricity transmission grid. Upper right: Peak current speed on a spring tide. Lower left: Light grey areas show water depths >40 m, areas further inshore are <40 m deep. Lower right: Sites identified by Black & Veatch, 2004 and MCT Ltd as suitable for tidal current turbine arrays. Source for all base maps: ABPMer et al., 2004.

Summary and conclusions This article has reviewed tide and wave energy resources and technologies that exploit them. For each resource, an interpretation of how these technologies could be deployed at large scale in UK waters followed.

68 Wave and tidal power Table 4.3 Summary of simplified UK resource assessment of wave and tidal current energy. Region

Shetlands Orkney Hebrides Islay/Kintyre N Ireland Wales SW England E England Total number of sites Installed capacity per farm (MW) Annual output per farm (GWh) Total installed capacity (MW) Total annual output (GWh)

Number of tidal current sites

Number of wave sites

With present grid

With grid upgrade

With present grid

With grid upgrade

0 11 1 1 4 3 4 1 25 133

4 11 7 6 4 4 9 2 50 133

0 4 0 0 0 2 2 0 8 30

6 4 19 1 0 2 4 0 36 30

466

466

53

53

3325

6650

240

1080

11.7

23.3

0.4

1.9

Pelamis is the leading WEC based on annual kWh produced/mass of device, although the Powerbuoy device may rank higher. The North Atlantic rated WaveDragon device produces more than any of the other devices, but suffers in the ranking because of its mass (33,000 tonnes). Costs associated with wave or tidal current technologies may be lowered by adopting the SeaSnail platform concept. This device replaces dead weight anchoring with hydroplane down-force, using a structure that is a fraction of the corresponding dead weight mass. In the UK, the accessible tidal energy resource is greater than the wave energy resource; although worldwide the wave resource is greater. With the current grid infrastructure, tidal current turbine farms with a total installed capacity of 3.3 GW may be foreseen, contributing around 11.7 TWh of electric power. Under the same conditions, the capacity of WECs could reach 240 MW, contributing around 0.4 TWh per annum of electric power. For both technologies, an important future barrier to exploitation is the proximity and accessibility of the transmission and distribution grid. Without a grid upgrade (particularly in Scotland) suitable sites may become rather scarce. Under this scenario, which would lead to areas such as Shetland, the Hebridean Islands, and some parts of south west Scotland being included in the accessible resource, installed capacity could total 6.6 GW for tidal current farms and 1.1 GW

Resources and further information

69

for wave farm developments. Annual yield would stand at 23.3 TWh for tidal power and 1.9 TWh for wave power respectively. The UK has set up a chain of useful facilities to support marine energy developments. The New and Renewable Energy Centre (NaREC) allows testing of physical models at small scale; the European Marine Energy Centre (EMEC) in Orkney provides facilities to test individual full scale prototypes; and the Wave Hub provides facilities for pre-commercial testing of arrays of wave power conversion devices. For the UK, the marine renewables sector is being driven by financial incentives. A similar situation exists in Portugal and to a lesser extent in the US where individual states offer specific incentives. A great deal of commercially driven development activity is thus emerging.

Resources and further information ABPMer, The Met Office, Garrad Hassan and Proundman Oceanic Laboratory, 2004. Atlas of UK Marine Renewable Energy Resources: Technical Report, A strategic environmental assessment report. Prepared for the UK Department of Trade and Industry, Project Ref No. R/3387/5, Report No. 1106. Alcorn, R., Hunter, S., Signorelli, C., Obeyesekera, R., Finnigan, T., and Denniss, T., 2005. Results of the Testing of the Energetech Wave Energy Plant at Port Kembla on October 26, 2005. Available at http://www.energetech.com.au/attachments/Results_ PK_Wave_Energy_Trial.pdf. Boyle, G. (ed), 2003. Renewable Energy, Power for a Sustainable Future, 2nd edition. Oxford University Press, Oxford. Bryden, I., Naik, S., Fraenkel, P., and Bullen, C.R., 1998. Matching tidal current plants to local flow conditions. Energy 23, 9, 699-709. Centre for Renewable Energy Sources (CRES), 2002. Wave Energy Utilisation in Europe, Current Status and Perspectives. Report from the European Thematic Network on Wave Energy. Available online at: http://www.cres.gr/kape/publications/download_ uk.htm. Dadswell, M. J., and Rulifson, R. A., 1994. Macrotidal estuaries: a region of collision between migratory marine animals and tidal power development. Bio. J. Linnean Soc. of London, 51, 1–2, 93–113. Discovery Channel, 2005, Video article on OPT Powerbuoy developments. [Online] http://www.exn.ca/video/?video=exn20051114-buoy.asx. Engineering Business Ltd, 2004. Project Summary: Stingray Tidal Stream Energy Device– Phase 3. Report number: M04-102-01. Available at: http://www.engb.com/Downloads/ papers/. Falnes, J., 2003. Principles for Capture of Energy from Ocean Waves. Department of Physics, Norges Teknisk Naturvitenskapelige Universitet (NTNU) (Norwegian University of Science & Technology) http://www.phys.ntnu.no/instdef/prosjekter/bolgeenergi/phcontrl.pdf. Accessed 10th April 2003.

70 Wave and tidal power

Gorban, A. N., Gorlov, A. M., Silantyev, V. M., 2001. Limits of the Turbine Efficiency for Free Fluid Flow. J. Energy Re. Tech. 123, 311–17. Gorlov, 2001. Tidal Energy. Conference paper available from http://www.gcktechnology. com/GCK/Images/ms0032%20final.pdf. Hagerman, G. 1995. A standard economic assessment methodology for renewable ocean energy projects. Proceedings of the International Symposium on Coastal Ocean Space Utilization, COSU, 129–38. Kerr, D. 2005. Proceedings of Institute of Civil Engineers, Civil Engineering 158, 32–9. Kirby R., and Shaw, T. L., 2005. Severn Barrage, UK—environmental reappraisal. Proc. Inst. Civ. Eng., Engineering Sustainability, 158, 31–9. Kofoed, J. P., Frigaard, P., Friis-Madsen, E., and Sørensen, H. C., 2004. Prototype Testing of the Wave Energy Converter Wave Dragon. Proc. 8th World Renewable Energy Cong., A. A. M Sayigh (ed). Denver, Colorado, Aug 28th - Sept 3rd 2004. Pidwirny, 2005. Fundamentals of Physical Geography, Chapter 8, Ocean tides. Online book available at: http://www.physicalgeography.net/fundamentals/contents.html Ponti di Archimede SpA, 2006. http://www.pontediarchimede.com/. Previsic, M., Bedard, R., and Hagerman, G., 2004. E21 EPRI Assessment, Offshore Wave Energy Devices. US Electrical Power Research Institute Report No. E21-EPRI-WP004-US-Rev1. Available online at: www.epri.com. [Accessed 09 Apr 2006] Takenouchi, K., Okuma, K., Furukawa, A., and Setoguchi, T., 2006. On applicability of reciprocating flow turbines developed for wave power to tidal power conversion. Renewable Energy, 31, 209–23. Teamwork Technology BV, 2004. http://www.waveswing.com/ [Accessed 25 May 2004] (Archimedes Wave Swing device) TideElectric, 2005. http://www.tidalelectric.com/Tidal%20Resource.htm WaveDragon ApS, 2006. http://www.wavedragon.net/.

The author Dean L. Millar is a senior lecturer at the Camborne School of Mines, University of Exeter. Originally trained as a mining engineer, practising in the UK and overseas, he specialized in geotechnical engineering and rock mechanics, lecturing in this subject at Imperial College London between 1993 and 1997. An interest in the coastal engineering applications of rock mechanics led to his appointment at the Camborne School of Mines in Cornwall, where he has conducted research into the use of abandoned mine shafts as oscillating water column wave energy conversion devices and wave energy resource assessment and impact. He maintains a broad interest in all aspects of renewable energy in addition to wave energy, particularly transport biofuels, and established the UK’s first undergraduate degree programme in renewable energy in 2003.

5.

Wind energy Bill Leithead Introduction Wind energy resource Public acceptance Technical development Concluding remarks Acknowledgement Further Reading

71 72 77 78 82 83 83

Introduction A wind turbine or even a wind farm, i.e. a group of wind turbines, is becoming an increasingly familiar sight in the countryside today. The wind turbine converts the power in the wind to electrical power and consists of a tower, rotor, typically with three blades as in Fig. 5.1, and a nacelle containing the power converter. From its rebirth in the early 1980s, wind power has experienced a dramatic development. Today, other than hydropower, it is the most important of the renewable sources of power. With an installed capacity equivalent to that required to provide electricity for over 19,000,000 average European homes and annual turnover greater than £5,500,000,000, wind energy has exceeded its year-onyear targets over the last decade. This growth in the contribution to electricity generation from wind power in Europe is likely to continue over the next few years, since the EU Commission has set a European target for 2010 of 12% of electricity generation from renewable sources. In the long term, the achievable limit to the contribution of wind power is estimated to be 30% of the total European demand, an amount almost equal to the installed nuclear capacity. In the UK, wind power is the fastest growing energy sector. Over 4,000 people are employed by companies working in the wind sector, and it is estimated by the UK Department of Trade and Industry (DTI) that the next round of offshore wind development could generate a further 20,000 jobs. In a 2003 Energy White Paper, the UK government aspired to achieving a 60% reduction in UK CO2 emissions

72 Wind energy

Figure 5.1 A typical modern wind turbine.

by 2050. In order to do so, it has set targets for UK electricity generation from renewable sources of 10% of electricity demand by 2010 and 20% by 2015. Since it is the most mature of the renewable energies, much of these near term targets must be met by wind power. Irrespective of whether these targets are achieved, the potential for increase in the UK is substantial. The prospects for wind power development in the UK are dependent on the available wind resource, public acceptance, and technical development. Each of these issues is discussed below.

Wind energy resource The power in the wind increases with the cube of the wind speed. Hence, the resource available at a specific location depends strongly on the annual mean wind speed. The European Wind Atlas, Fig. 5.2, indicates on a large scale those regions with similar annual mean wind speed. However, the annual mean wind speed at a specific location depends strongly on the local topography and may vary considerably from the regional mean. It should also be noted that the annual

Wind energy resource

73

500 km

Wind resources at 50 metres above ground level for five different topographic conditions Sheltered terrain > 6.0 5.0-6.0 4.5-5.0 3.5-4.5 < 3.5

> 250 150-250 100-150 50-100 < 50

At a sea coast

Open plain > 7.5 6.5-7.5 5.5-6.5 4.5-5.5 < 4.5

> 500 300-500 200-300 100-200 < 100

> 8.5 7.0-8.5 6.0-7.0 5.0-6.0 < 5.0

> 700 400-700 250-400 150-250 < 150

Open sea > 9.0 8.0-9.0 7.0-8.0 5.5-7.0 < 5.5

> 800 600-800 400-600 200-400 < 200

Hills and ridges > 11.5 10.0-11.5 8.5-10.0 7.0-8.5 < 7.0

> 1800 1200-1800 700-1200 400-700 < 400

Figure 5.2 European on-shore wind atlas.

mean wind speed increases with the height above ground of the measurement; for example, the difference in annual mean wind speed between a height of 40 m and 60 m is approximately 10%. Hence, the resource at a specific site depends strongly on the locality and the size of wind turbines to be installed. Nevertheless, general trends hold, with the annual mean wind speed increasing to the north and to the west. With an annual mean wind speed of roughly 7 m/s for England and Wales and 8 m/s for Scotland, the UK clearly has a very rich resource compared to other European countries. To emphasize this fact, it is sometimes claimed that

74 Wind energy

the UK has 40 % of the European wind resource. Of course, this claim is highly subjective, being dependent on the details of the resource estimation and the definition of Europe used, and should be interpreted merely as indicative of the comparative richness of the UK resource. Not all of the wind power resource can be realized however. Wind farms must be sited in open country avoiding sites of scientific interest and sufficiently far from inhabited buildings and roads. Unfortunately, much of the exploitable resource is located to the north and west, far from the main population centres. To fully exploit this resource would require the transmission of large amounts of electrical power over long distances from the points of generation to the points of consumption. The national grid is currently not well placed to accommodate this transmission because of such restrictions as the capacity of the inter-connector between Scotland and England. The European Offshore Wind Atlas, Fig. 5.3, has a similar pattern to Fig. 5.2. Again, the wind power annual mean wind speed increases to the north and west, with the UK well resourced. The resource that can be exploited must be in shallow water and away from major shipping lanes. Even with these restrictions, there is a large exploitable resource off the north west, south east and south west coasts of England. These have the advantage of not being far away from the large centres of population, and so may be particularly valuable. In particular, there is a considerable offshore resource round the southern part of England. For example, from Fig. 5.2 and 5.3, the annual mean wind speed at a height of 50 m on the sea coast round England is 7–8.5 m/s and 10 km offshore at a height of 100 m is 8.5–10 m/s. Sites with these wind speed attributes would be sufficiently well resourced for exploitation. In comparison to the UK’s annual electricity demand of roughly 350 TWhours/year, it would be technically feasible, but not practical, to generate 1,000 TWhours/year of electricity from wind. Instead, the accessible and economic resource is approximately 150 TWhours/year. Onshore wind power could contribute in the region of 50 Twhours/year and offshore wind power could contribute in the medium term 100 Twhours/year. From the above discussion, it is clear that the UK wind power resource is particularly strong in comparison to other European countries. However, the UK record in exploiting that resource is relatively poor. The very rapid growth in wind power capacity installed in the EU is shown in Fig. 5.4. By 2005, it stood at 35 GW, constituting 70% of the world total. The USA accounts for much of the non-European capacity. The contributions to the total EU installed capacity by the leading countries, Germany, Spain, and Denmark, are 16,629 MW, 8,263 MW, and 3,117 MW, respectively, followed by Italy, the Netherlands, and the UK, with 1,125 MW, 1,078 MW, and 888 MW. Although it is increasing rapidly, the UK installed capacity is rather modest in comparison to Germany, Spain, and Denmark, especially when the extent of the resource is taken into account

Wind energy resource

75

500 km

Wind resources over open sea (more than 10 km offshore) for five standard heights 10 m > 8.0 7.0-8.0 6.0-7.0 4.5-6.0 < 4.5

> 600 350-600 250-300 100-250 < 100

25 m > 8.5 7.5-8.5 6.5-7.5 5.0-6.5 < 5.0

> 700 450-700 300-450 150-300 < 150

50 m > 9.0 8.0-9.0 7.0-8.0 5.5-7.0 < 5.5

> 800 600-800 400-600 200-400 < 200

100 m > 10.0 8.5-10.0 7.5-8.5 6.0-7.5 < 6.0

> 1100 650-1100 450-650 250-450 < 250

200 m > 11.0 > 1500 9.5-11.0 900-1500 8.0-9.5 600-900 6.5-8.0 300-600 < 6.5 < 300

Figure 5.3 European offshore wind atlas.

(see Figs. 5.2 and 5.3). To highlight this, the contribution of wind-generated electricity to the total annual consumption for several EU countries is listed in Table 5.1., where the absolute values are given together with the wind generation as a percentage of the annual consumption. In terms of the latter, only in Denmark, Spain, and Germany does wind power contribute significantly towards electricity supply. In addition, the fraction of the potential, i.e. the accessible and economic resource, exploited to date, is listed in Table 5.1. The UK is only exploiting 1% of the usable resource. It might be expected that the explosive growth of wind power indicated by Fig. 5.4 would be accompanied by a reduction in the cost. The price of wind turbines in D/kW is also shown in Fig. 5.4 and confirms the expected

76 Wind energy Table 5.1 Wind generation for several EU countries.

Austria Denmark France Germany Spain UK Total

Annual Consumption (TWh)

Wind Generation (TWh)

Wind Generation %

60.15 81.73 431.86 531.78 221.42 349.20 2562.7

0.24 5.28 0.20 18.49 11.95 1.45 42.60

0.4 6 0.04 3.47 5 0.4 1

Fraction of Potential % 8 18 0.2 77 14 1 6.6

× 104 4

4000

Wind Turbine Price (Euro/kW)

3000

3

2000

2

1000

1

0 1980

1985

1995

1990

2000

Installed Capacity (MW)

Installed Capacity

Wind Turbine Price

0 2005

Year

Figure 5.4 Growth of installed capacity and reduction in price.

reduction. It is due in part to improvements in the technology but mainly to economy of scale derived from large-scale production. As a result, the price of electricity generated by wind power is now becoming competitive. Although the price is development specific, it is approximately 4.5–6.0 cD/kW hour for onshore wind farms. The price for offshore wind farms is estimated to be 50% higher. For comparison, the price of electricity for new coal generation plant is approximately 3.8–6.8 cD/kWhour and, for a new nuclear generation plant, 6.0– 10.5 cD/kWhour. Associated with the generation of electricity are external costs

Public acceptance

77

that are not accounted for in the price figures quoted above. These include the cost of environmental impact and decommissioning of the plant. The external costs for wind power are equivalent to 0.26 cD/kWhour. The corresponding figure for conventional coal generation, although heavily dependent on the assumptions made concerning the environmental costs related to carbon emission, is 2– 15 cD/kWhour. Furthermore, the scrap value of the wind turbines pays for decommissioning, and the energy payback time— i.e. the time taken to generate the quantity of power used during the manufacture and installation of a wind turbine—is only 3 to 10 months. In other words, over a lifetime of 20 years, the power produced is at least 24 times the power consumed during its manufacturing and installation. Wind power is already almost cost competitive with conventional sources of electricity generation and will become increasingly so as the latter become more expensive in the future.

Public acceptance Whenever a wind farm development is proposed, concerns arise over its impact on the local environment. Three issues that are usually raised are noise, the effect on birds, and visual intrusion in the landscape. These are not entirely amenable to a technical solution, as perception of them is to some extent subjective. Public acceptance of wind power depends on a sensitive response by the industry. Noise emitted by wind turbines has two main sources, mechanical noise and aerodynamic noise. The source of mechanical noise is largely the gearbox. It may be amplified through resonating with the tower. However, in a well-designed wind turbine, it can be reduced to an unobtrusive level through improved damping and insulation of the gearbox and modification of the resonance characteristics of the tower. The aerodynamic noise is at low frequency and is dependent on the rotational speed of the wind turbine rotor. In high wind speeds, it is masked by the ambient noise but, at low wind speeds, it is more apparent. Some reduction in aerodynamic noise has been achieved through improvement to the aerodynamic design of the wind turbines and through operating the machines with lower rotational speeds in low wind speed. The latter strategy is being adopted on most modern wind turbines. The measured noise level of a 1 MW wind turbine at 300 m is 45 dB. It is less noisy than a vacuum cleaner at 30 m, which is measured at 50 dB, in other words, ‘half as noisy’. However, the characteristics of a noise are also important to its perception, and wind turbine noise is perceived by some people to be more intrusive than other sources. Indeed, the awareness of wind turbine noise varies greatly and appears to be partly psychological. There are concerns that wind farm developments will result in the deaths of many birds from collisions with the machines. Data for bird strikes are available from countries with an established wind industry. During 2003, there were 88

78 Wind energy

deaths of medium and large birds caused by 18 wind farms in Navarra, Spain; that is, the annual mortality rate is 0.13 birds/turbine or, on average, a wind turbine kills a bird every seven years. In Finland with 82 MW of installed capacity, during 2002, there were 10 bird fatalities from collision with wind turbines, compared to 820,000 birds killed annually from collision with other artificial structures (cars, buildings, etc.). In the USA, during 2002, there were 33,000 bird fatalities due to wind turbines, but 100 million to 1,000 million from collisions with artificial structures. In the UK, domestic cats are thought to kill 55 million birds annually. Further evidence in support of these low fatality rates is obtained from visual observation and radar observation studies of bird flight. It is observed that, when flying through a wind farm, birds tend to avoid the turbines, keeping as far away from them as possible. Nevertheless, concern over the impact of wind farms on birds remains, not necessarily due to the fatalities, but due to habitat loss through displacement of the birds. A common perception is that, for wind power to make a substantial contribution to the UK energy needs, large numbers of wind turbines occupying an extensive part of the countryside are required. The result would be a great loss of amenity due to visual intrusion in the landscape. However, the number of machines involved is frequently exaggerated. Just 600 modern 5 MW wind turbines would be sufficient to replace 1,000 MW of conventional generation; that is, to supply 20% of the peak Scottish electricity demand. To locate sufficient wind farms to provide 10% of the UK’s electricity needs would require a land area of 30 km by 40 km, less than 0.5% of the land area of the UK. Furthermore, the land used for a wind farm is not excluded from other use, e.g. agricultural land would remain so except for a small footprint round the base of each turbine and the access roads to the wind farm. Hence, even with large-scale development, the land that would be occupied by wind farms is not overly extensive, particularly since a substantial part is likely to be sited offshore and, thereby, rendered less visually intrusive. The visual impact of offshore wind farms quickly diminishes with distance, and 10 km would suffice. Nevertheless, although past experience indicates that public acceptance tends to increase after installation, visual intrusion is likely to remain an issue for some people. Perhaps the concerns related to the public acceptance of wind farms, specifically, noise, the effect on birds, and visual intrusion in the landscape, are somewhat exaggerated. However, they will persist, especially as the concerns are partly subjective, and the wind energy industry will need to respond sensitively.

Technical development There are many aspects of technical development that impinge on the prospects for wind power development in the UK. These include turbine evolution, turbine availability, wind variability, grid connection and radar, and electromagnetic

Technical development

79

interference. Each will be discussed briefly below. In addition, the challenge to adapt the technology to the offshore environment is considered. The dominant type of wind turbine is the so-called Danish concept. It is a three bladed horizontal axis up-wind machine; that is, the rotor faces into the wind and rotates in a vertical plane. The generator is indirectly connected to the electrical grid through power electronics, thereby enabling the wind turbine rotor rotational speed to vary within some prescribed range. This facility is used to reduce the mechanical loads on the turbine and, in low wind speeds, to improve the aerodynamic efficiency and, most importantly, reduce aerodynamic noise. The blades can be pitched about their longitudinal axes to feather the blades and regulate the rotational speed of the rotor. For obvious reasons, this type of wind turbine is called a variable speed pitch regulated wind turbine. Wind turbine technology has evolved rapidly over the last twenty years. The most obvious manifestation of this development is the exponential increase in machine size, see Fig. 5.5. In 1980, a large wind turbine had a rotor diameter of 20 m and a rated power, i.e. maximum generated power, of 50 kW. Today, a large wind turbine has a rotor diameter of 120 m and a maximum generated power of 5 MW. In addition to becoming much larger, wind turbines have become more efficient. Since the wind speed varies, a wind turbine cannot produce rated power all

5000 kW Ø 124m

2000 kW Ø 80m 600 kW Ø 50m 500 kW Ø 40m

50 kW Ø 15m

1980

100 kW Ø 20m

1985

1990

1995

2000 2003

Figure 5.5 The growth in wind turbine size, 1980 to 2003.

80 Wind energy

the time. In the lowest wind speeds, the wind turbine is shut down since the power extracted from the wind is less than the internal losses. Above this lowest wind speed, the power produced increases with wind speed until the maximum power level of the wind turbine is reached. The power is then held constant at this maximum, except in the highest wind speeds when the wind turbine is again shut down. Consequently, the annual average power output from a wind turbine is much less than the rated power. A section of power generated by a 2 MW wind turbine in low wind speed is depicted in Fig. 5.6. The average power is measured by the capacity factor: the ratio of the average power to the rated power. In 1986, the typical target capacity factor for wind turbines was about 0.27 but the achieved capacity factor might be as low as half that value. The reason for this poor operational efficiency was the lack of reliability of some machines. Today wind turbines are much more reliable, attaining an availability in excess of 98%; that is, 98% of the time the turbines are capable of generating power provided the wind speed is not too low. On a good site, the capacity factor for a modern wind turbine is about 0.3 and sometimes even higher.

Generated power 700

650

Power (W)

600

550

500

450

400

0

100

200

300 Time (sec)

Figure 5.6 Power output in low wind speeds.

400

500

600

Technical development

81

Because, as mentioned above, the wind speed varies causing the power output from a wind turbine to fluctuate, the value of wind power is sometimes questioned. It is argued that conventional generation with the same rating as the installed capacity of wind power, must be kept available in reserve to cover any deficit between electricity supply and demand. However, all electricity generation and supply systems require back-up including spinning reserve; that is, generators that are kept running and available to supply power at short notice. This reserve is necessary to cover any unexpected drop in electricity supply that might arise from a fault or loss of a large generation station. It is also required to cover any unexpected rise in electricity demand. The demand is partially predictable but an unpredictable residue that can be considered random, remains. On a local level, this residue may not be small but it is made much less significant by aggregation over the whole network. Similarly, the variability of wind power is much reduced by large-scale aggregation; that is, by having the wind farms distributed over a large geographical area. The aggregated wind power can again be considered as partially predictable, through exploiting weather forecasting information, with an unpredictable random residue. To accommodate wind power on an electricity supply network, it is treated as negative demand. The variability of demand is thus increased as it now includes the variability in the wind power. Sufficient generating back-up capable of covering this increased fluctuation in the electricity demand must be maintained. With the current very low level of wind power penetration in the electricity supply system, no increase in back-up is required. With a 10% penetration of wind power, only 300–500 MW of additional conventional back-up would be necessary. Even with all the costs of this extra back-up attributed to wind power, it is equivalent to adding only 0.3 cD/kWhour to the price. The electricity supply system is not traditionally designed to accommodate generation distributed throughout the network, which would be the case with significant amounts of wind power. Instead, it is designed for large-scale central generation of power with outward transmission and distribution through the network. Nevertheless, the existing grid is expected to cope with 20% wind power penetration, although larger penetration would require its reconfiguration. In addition, there are concerns that wind power might reduce the stability of the grid, for example, through a fault propagating through the network causing wind turbines to serially disconnect. However, this issue is being addressed through the stipulation of appropriate grid connection codes for wind turbines. The wind turbine manufacturers are confident of their ability to meet these codes. Wind turbines can have an adverse effect on communication systems and radar systems through electromagnetic interference. In communication systems, the transmitter or receiver must be in close proximity to the wind turbines. In radar

82 Wind energy

systems, the interference is more serious but it can be countered by advanced filtering algorithms. The UK has a rich offshore wind resource and it is expected that offshore development will be a major component of the UK’s wind power development programme. The advantages of offshore development of wind power are considerable. The wind speeds are higher and the turbulence levels are lower than onshore. The visual intrusion, if not absent, is much less and there are no noise restrictions. In the absence of the latter, the wind turbines can be operated at higher rotor rotational speeds and so with lower loads. However, there are several disadvantages. There are higher capital costs because more substantial foundations are required offshore than onshore and because of connection by subsea electrical cable to the shore. Access to offshore wind turbines is restricted by poor weather conditions, in particular, strong winds or high seas. Consequently, operation and maintenance (O&M) costs are increased. As a fraction of the income of a wind farm, the O&M costs are approximately 10% to 15% onshore but are estimated to be 20% to 25% offshore. The technical challenge is to make offshore wind power more cost-effective by reducing the cost of O&M through improved reliability and proactive maintenance and by increasing yet further the size of wind turbines. The extent to which the latter can be achieved is not clear. Indeed, it may not be practical to make turbines much bigger than the existing maximum of 5 MW.

Concluding remarks The price of wind power is almost competitive with conventional means of electricity generation. The UK has a rich exploitable wind power resource, particularly, towards the north and west of the country, but also round the south coast of England close to the main population centres. Although it is well established in Europe—and is making a significant contribution to electricity supply in Denmark, Spain, and Germany—wind power is still embryonic in the UK. Nevertheless, it is feasible that it could meet 10% of the UK’s electricity demand. Such a large expansion would raise public concerns that include noise, impact on birds, and visual intrusion in the landscape. These concerns have a subjective element and are perhaps overstated, but large-scale development would need to be treated sensitively. To avoid difficulties over the public acceptance of wind power, offshore development would be preferable to onshore development and it is expected that offshore wind power will make a major contribution in the UK. In these circumstances, wind energy technology would enter a new era with many technological challenges. To conclude, wind power could make a major contribution to the UK’s energy needs. The only major obstacle might be lack of political will.

The author

83

Acknowledgement Fig. 5.1 is reproduced with permission from the BWEA and Figs. 5.2 and 5.3 from Risø National Laboratory, Roskilde, Denmark.

Further Reading General information on wind energy can be found in the following publications: EWEA, 2004. Wind Energy–The Facts–an Analysis of Wind Energy in the EU-25, (available at http://www.ewea.org/index.php?id=91). BWEA, 2005. Top Myths about Wind Energy, (available at http://www.bwea.com/energy/myths.html). UK DTI, 2001, The UK Wind Resource: Wind Energy Fact Sheet 8, (available at http://www.dti.gov.uk/renewables/publications/pdfs/windfs8.pdf). UK DTI, 2003, Our energy future—creating a low carbon economy, Energy White Paper (available at http://www.dti.gov.uk/energy/policy-strategy/energy-white-paper-2003/ page21223.html) An introductory text to wind energy technology is T. Burton, D. Sharpe, N. Jenkins, E. Bossanyi. 2004. Wind Energy Handbook , John Wiley & Sons Ltd., London. Troen, I. and Peterson, E. L. 1989, European Wind Atlas, Riso National Laboratory, Roskilde.

The author Bill Leithead is Professor of Control and Systems Engineering at the University of Strathclyde. He has been actively involved in wind energy both through academic research and collaboration with industry since 1988. He has published extensively on wind energy and has worked with many European manufacturers. Professor Leithead is currently on secondment to the Hamilton Institute in Ireland.

6.

Nuclear fission Sue Ion∗ Introduction The physics of fission The policy context Cutting carbon emissions Economics Reliability of electricity supplies Potential new reactor technology Investor considerations—regulation Investor considerations—delivery and operational performance Investor considerations—waste Investor considerations—the electricity market Public attitudes The longer term future

84 84 86 87 88 90 93 97 97 99 101 101 102

Introduction This chapter will cover the nuclear fission option as a future energy supply, and will essentially address the question: can nuclear fission plug the gap until the potential of nuclear fusion is actually realized? (The potential for fusion is considered in detail chapter 7.) To put this question into context, let us first look at some of the key issues associated with nuclear fission, which currently supplies around one fifth of the UK’s electricity.

The physics of fission Most large scale power stations produce electricity by generating steam, which is used to power a turbine. In a nuclear power station, the principle is the same, but ∗ The

author gratefully acknowledges the contribution and assistance of Adrian Bull in the preparation of this chapter.

The physics of fission

85

instead of burning coal, oil, or gas to turn water into steam, the heat energy comes from a nuclear reactor. A reactor contains nuclear fuel, which remains in place for several months at a time, but over that time it generates a huge amount of energy. The fuel is usually made of uranium, often in the form of small pellets of uranium dioxide, a ceramic, stacked inside hollow metal tubes or fuel rods, which can be anything from a metre to four metres in length, depending on the reactor design. Each rod is about the diameter of a pencil, and the rods are assembled into carefully designed bundles, which in turn are fixed in place securely within the reactor. There are two isotopes (or different types) of uranium, and only one of these is a material which is ‘fissionable’—that is to say, if an atom of this uranium isotope is hit by a neutron, then it can split into two smaller atoms, giving off energy in the process and also emitting more neutrons. This, and other pathways, are illustrated in Fig. 6.1 (Source: CEA). Controlling the reaction, so that the energy from the fission of uranium atoms is given out slowly over a period of years, requires two aspects of the process to be carefully balanced.

Gamma radiation

Third generation neutrons

Gamma radiation Second generation neutrons Fissile nucleus of uranium-235

Incoming neutron

Fission products

Fissile nucleus of uranium-235 Fissile nucleus of uranium-235

Fission products

Gamma radiation Figure 6.1 Schematic diagram of fission of 235 U

Fission products

86 Nuclear fission

1.

First, there must be enough fissile atoms in the fuel so that—on average— each fission leads to exactly one other. Any fewer, and the reaction will die away. Any more, and the reaction will speed up very rapidly and would—if not brought back under control—generate too much heat and damage the integrity of the fuel. The number of fissile atoms is controlled by ‘enriching’ the uranium to the right level when the fuel is fabricated. The fissile isotope of uranium (235 U) is just 0.7% of naturally occurring uranium, and this proportion is increased to around 3 or 4% during the enrichment process. Once enriched, the uranium is made into fuel pellets, as described above.

2.

Second, the neutrons must be slowed down or ‘moderated’if they are to cause fission to take place. If they are moving too fast, they essentially by-pass any uranium atoms they might come across. The moderation occurs as the neutrons pass through materials such as graphite or water. Different designs of reactor use one or other of these materials in the heart of the reactor core to slow the neutrons down. In a modern pressurized water reactor (PWR), the water also acts as the coolant—passing over the fuel to remove the heat. In older designs, such as Magnox or Advanced Gas-Cooled Reactors (AGRs), much of the reactor core is made up of graphite blocks, and the heat is removed by passing gas over the fuel rods.

Overall control of the nuclear reaction is maintained by means of removable ‘control rods’. These are made of materials such as boron, which essentially ‘soak up’neutrons in the reactor. The control rods can be lowered into the reactor core to slow down the reaction, or stop it all together. As the 235 U in the fuel is gradually used up over a period of months and years, the precise positioning of the control rods can be adjusted to compensate for this, by absorbing slightly fewer of the neutrons. In this way, the uranium fuel provides a steady supply of heat to the coolant, as the reactor operates. This in turn is converted into electrical energy via the turbine. A single modern nuclear reactor can provide around 1,000 MW or more of electrical energy continuously to the power transmission grid. The policy context Back at the time when the Energy White Paper was launched in early 2003, the UK government identified four key pillars of energy policy. Environmental acceptability, reliability, affordability, and competition in the market. Never stated—but implicit—was a fifth pillar, namely the safety of whatever technologies might be deployed, both to the workforce and the wider public. The White Paper provided no overt support for nuclear fission, but did recognize the

Cutting carbon emissions 87

potential contribution it could make through its low carbon emissions. However, it also noted some issues associated with nuclear energy, in terms of the economics and in terms of waste, both of which, it was felt, needed resolution.

Cutting carbon emissions In terms of the environment, the consideration which is perhaps the most important is the emission of CO2 , and Fig. 6.2 shows the comparison of nuclear with gas and coal in this respect. The coal figure reflects coal without sequestration, and the figure for gas is for North Sea gas. If the UK’s gas were to come from overseas—in whatever way— there would be additional energy associated with its transport, and thus additional emissions. Although these might not occur within the UK, they obviously still contribute to global climate change. Recognizing the UK’s strong historical usage of coal, and the benefits it offers in terms of flexibility and reliability, we must consider generation from coal with capture and storage of the associated carbon dioxide as a key component of the future electricity mix. It is also important to note that in terms of CO2 emissions, nuclear and wind power are actually rather similar. Both are dramatically lower than either coal or gas. At a time when CO2 emissions are rising this is a vitally important consideration.

1000 900 800 Kg CO2/kWh

700 600 500 400 300 200 100 0 Coal-fired power stations

Gas-fired power stations

Nuclear

Figure 6.2 Typical carbon dioxide emissions from coal, gas, and nuclear stations.

88 Nuclear fission

Economics When we look at how the economics of nuclear energy compare with other alternatives, there are inevitably a whole host of discussions to be had about key assumptions such as the rate of return which an investment must deliver, the length of time the plant will last, its performance, fuel costs, and so on. These apply not just to nuclear stations, but to the other options too, and it is unlikely that there will ever be definitive agreement on these issues between proponents of the various options, or indeed between energy market analysts. However, it is still instructive to look at the broad conclusions of recent authoritative studies, as these give a helpful indication of the relative economics. One such study—looking at a whole range of figures from around the world, was carried out earlier this year by the Organization for Economic Development (OECD) in conjunction with the International Energy Agency (IEA) and the Nuclear Energy Agency (NEA)—see Fig. 6.3. Importantly, this looked at a range of input assumptions and specifically looked at two different rates of return—5% and 10%. The chart clearly shows that nuclear is the cheapest option under either assumption, and whilst I am not going to argue that this in itself demonstrates nuclear would be the cheapest option in the UK, it is difficult to conclude that it would not be there or thereabouts in comparison with the leading fossil fuel alternatives. When we come to look in more detail at the ways in which we can cut carbon emissions, it is important to note also that nuclear is coming in at a much lower cost than renewables such as wind.

Generating cost £/MWh

140 5% Rate of return Lower limit 10% Rate of return Lower limit

120

Range Range

100 80 60 40 20 P H C

la r So

in d ic ro -h yd ro M

W

ar N

uc le

as G

C

oa l

0

Source: ‘‘Projected Costs of generating Electricity’’, OECD; March 2005

Figure 6.3 Cost projections from OECD study: ‘Projected costs of generating electricity’, March, 2005.

Economics

89

8.0 Standby generation cost

7.0 6.0

Cost of generating electricity

5.0 4.0 3.0 2.0 1.0

Wave & Marine

Offshore Wind-Farm

Onshore Wind-Farm

Poultry-litter BFB

Nuclear

Gas-fired CCGT

Gas-fired OCGT

Coal-fired IGCC

Coal-fired CFB

0.0 Coal-fired PF

Cost of generating electricity (p/kWh)

Like the OECD study, the Royal Academy of Engineering concluded in 2004 that nuclear was very competitive in cost terms to gas, and much cheaper than renewables. This conclusion (illustrated in Fig. 6.4) was reached even before any allowance was made for the costs associated with carbon emissions. When those were included, the economics of nuclear were shown to be far and away the cheapest. The pedigree of those studies illustrates that nuclear should not be discounted on the grounds of its economics. A further feature of nuclear energy relates to the stability of its economics. The cost of the finished fuel assemblies accounts for around 20% of the overall nuclear generating cost, and of this around a quarter— 5%—is the cost of the raw uranium. The other 15% is associated with enrichment and fabrication costs. This is in stark contrast to, say, gas-fired generation, where the cost of the raw gas is typically 60% or so of the overall costs (see Fig. 6.5). That means that if the world market price of gas were to double (and that’s by no means inconceivable, based on recent experience) the cost of gas-generated power would go up by 60% immediately. Yet if the world market price of uranium were to double, the impact on power costs from nuclear stations would be a mere 5%. Even this impact would not be felt for a year or so, when any newly purchased uranium had found its way to the power station in the form of fuel.

Source: ‘‘The Cost of Generating Electricity’’; RAE March 2004

Figure 6.4 Cost projections from Royal Academy of Engineering Study: ‘The cost of generating electricity’, March, 2004.

90 Nuclear fission

100% 80% Capital 60% 40% O&M 20% Fuel 0%

Nuclear

Coal

Natural gas

Figure 6.5 Relative contributions of capital, operation, and maintenance and fuel costs for different generation options.

Reliability of electricity supplies But it is not just in terms of economics that nuclear offers reliability benefits. There is growing concern over the ability of two technologies to provide reliable power over the coming decades. These technologies are gas and renewables—in particular wind power—two forms which are projected to account for much of the UK’s generating portfolio over future years. Consider the following combination of issues which the UK is currently facing: •

The UK is in the midst of the ‘dash for gas’—a huge shift in our power generation portfolio, which has seen us move from 65% coal-fired power in 1990, with no gas stations at all, to a position where we now expect at least two thirds of our power in 2020 to come from gas (see Fig. 6.6).

•

The UK’s nuclear fleet has already begun its progressive programme of station closures and is the first country in the world to be in this position, not due to any deficiencies in the fleet, but simply because the UK led the world in adopting nuclear in the first place. Fig. 6.7 shows how the next 10–15 years are likely to see most of the current fleet reach the end of its life.

• At the same time as the UK nuclear fleet is closing, it faces the prospect of

losing a large tranche of our coal fired stations as well—due to the EU Large Combustion Plant Directive, which forces older coal plants either to close by 2015 or else to retro-fit equipment to clean up the discharges from such stations. •

Not only are global oil and gas reserves looking increasingly limited as demand increases, but the UK’s domestic oil and gas reserves are well on

Reliability of electricity supplies

Actual

91

Forecast

400 350 300 TWh

250 200 150 100 50 0

1990 1992 1994 1996 1998 2000 2001 2002 2003 2005 2010 2015 2020 Gas Coal Oil Nuclear Renewables10 Imports and other Gas increase11 Renewables increase11 10 Includes hydro except pumped storage. 11 Increases are from the 2000 level.

Source: DTI/Ofgem JESS report: November 2004 Figure 6.6 Historic and projected future power generation mix in the UK. (Source: DTI/Ofgem figures)

10000 9000 8000

Capacity MWe

7000 6000 5000 4000 3000 2000 1000

20 0 20 4 0 20 5 0 20 6 0 20 7 0 20 8 0 20 9 1 20 0 1 20 1 1 20 2 1 20 3 1 20 4 1 20 5 1 20 6 1 20 7 1 20 8 1 20 9 2 20 0 2 20 1 2 20 2 2 20 3 2 20 4 2 20 5 2 20 6 2 20 7 2 20 8 2 20 9 3 20 0 3 20 1 3 20 2 3 20 3 3 20 4 35

20

03

0

Figure 6.7 Projected fall in UK nuclear generation capacity.

92 Nuclear fission

the way to being depleted. The UK became a net importer of gas again in 2004, and as its reliance on gas rises, it could be importing up to 80% of its gas needs by 2020, by which time gas will be the dominant component of the mix. Such long term dependence on imported gas, with risks attached to both source and pipeline route, is a precarious situation for any nation. Disruption along any part of the route could put supplies in jeopardy. There is an increasing emphasis being placed on both renewables and energy efficiency—both themes of the 2003 Energy White Paper. Both have a substantial role to play, but both present their own challenges: •

New renewable energy is mainly wind at present, and for the foreseeable future. This is inherently intermittent, and experience in countries such as Denmark and Germany, which have deployed substantial quantities of wind generation, has shown it to require substantial backup capacity if a reliable power supply is to be expected. The UK government has set an aspiration of 20% of the UK’s electricity to come from renewables by 2020— a hugely ambitious objective. Yet even if this were to succeed, it would just offset the closure of carbon-free nuclear plants on approximately the same timescale, meaning that there would be no improvement in emission terms.

•

Energy efficiency has—like renewables—a positive contribution to make, but huge step changes in demand as a result of energy efficiency measures should not be anticipated. A key limiting factor is that energy saving measures are most viable when fitted in new properties. Retro-fitting is usually much less cost effective. Yet the turnover rate of homes and commercial property is measured in decades, so rapid improvements are unlikely.

•

The UK’s electricity market is newly–liberalized and there is a need to gain confidence that the market will provide the necessary signals to prompt new investment in good time to meet demand.

• And finally unlike virtually all of its major economic competitors, the UK

is essentially an island nation. There are very limited links to neighbouring nations for providing either raw fuels (coal, oil, and gas) or electricity via a network of power lines. The power link to France provides about 2 gigawatts worth of (largely nuclear) electricity. So looking to the short and medium term future the UK is set for a period of substantial change and needs to consider how nuclear energy can contribute to the reliability of supplies.

Potential new reactor technology 93

First, and most obviously, looking at a future dominated by gas and renewables, anything else—including nuclear—contributes to increased diversity, which must of itself be helpful in reducing risk. Without new stations, nuclear will be providing just 3% of UK electricity in under 20 years time, compared with around 20% today. Uranium is plentiful as a raw material, and comes from stable countries like Australia and Canada. Reliable baseload generation is a key feature of nuclear energy. Nuclear stations operate round the clock, day in and day out, irrespective of weather conditions. Apart from a periodic and predictable maintenance shutdown, the stations operate continuously at full power, providing the kind of baseload power a leading twenty-first-century economy demands. Furthermore, it is highly credible to retain strategic stocks of nuclear fuel, just in case there ever were to be any sustained disruption to supply. The fabricated fuel to supply a fleet of ten new reactors (enough to supply 20% of UK electricity needs) for a year, would occupy only around 100 cubic metres. That means it would be small enough to fit comfortably within a very modestly-sized house. Finally—as mentioned earlier—nuclear provides valuable cost stability as well as supply reliability.

Potential new reactor technology Let us now consider what technology would be available to the UK to move forward with nuclear. There are many options around the world at the moment. Interestingly, none of them have their genesis in the UK, unlike the systems currently operated which, with the exception of Sizewell B, are ‘home grown’ designs (see Table 6.1). The most likely options for the UK, were new nuclear to go ahead, are the European Pressurized Water Reactor, which is a Franco-German product, and the Westinghouse AP1000, which is an American product. The EPR design has already been selected in two countries—in Finland, where it is already under construction, and in France. The AP1000 is the lead candidate in the US for delivery. Both products are in head-to-head competition in China for four units. China already has a significant amount of nuclear capacity, mainly based on French and Canadian technology. Several other options on the table are being built in the Asia-Pacific basin. The EPR design is an improvement on the existing systems operating in Europe, with many safety features added, and enhanced protection against aircraft and earthquakes. These improvements were driven by the requirements of the European Utilities Requirements in the mid-1990s. It has some impressive technological advantages, but nevertheless is still considered proven, because it is

Table 6.1 Nuclear reactor technology currently under construction or consideration worldwide Reactor Design

Type

Country of Origin

Lead Developer

Development Status

ABWR CANDU-6 VVER-91/99 AHWR APR-1400 APWR EPR AP1000 SWR ESBWR ACR

BWR PHWR PWR PHWR PWR PWR PWR PWR BWR BWR PHWR

US Japan Canada Russia India Korea, US Japan France, Germany US France, Germany US Canada

GE, Toshiba Hitachi AECL Atomstroyexport Nuclear Power Corporation of India Kepco Westinghouse & Mitsubishi Framatome ANP Westinghouse Framatome-ANP GE AECL

Operating in Japan. Under construction in Japan & Taiwan Operating in Korea, China, Under construction in China Starting construction Planned for Shin-Kori Planned for Tsuruga Under construction in Finland Planned in France Licensed in USA Offered in Finland Under development Under development

Potential new reactor technology 95

Figure 6.8 Impression of the EPR Plant currently under construction at Olkiluoto, Finland.

actually based on existing technology (the N4 design) that is operating in France today, and the Konvoi reactors in Germany. Fig. 6.8 shows an impression of what the EPR will look like once completed in Finland, alongside the existing plants on the same site. The new reactor is due to be delivering power within five years. The French demonstrator of the same technology will follow soon after, with the expectation of a further fleet to follow in France. The AP1000, the American competing product, is again designed to meet the energy markets of the twenty-first century. It embodies safe, passive systems— with a lot of simplicity in the design, which is key to the economic benefit. In terms of economics, it is certainly competitive with the latest CCGT gas technology. Again—like the EPR—AP1000 uses proven components such as the plant’s steam generators, the pressure vessel and the pumps are already in operation in different reactors worldwide (see Fig. 6.9). On the economics, one might well ask how confident can the industry be that they will be competitive. We know how many components and how much material in terms of concrete, pumps, valves, and so forth, went into Sizewell B. And in comparison we know how many of the same items will go into a new design such as an EPR or AP1000. The difference, shown in Fig. 6.10 for the AP1000, is striking—largely due to the passive safety systems and associated simpler design. It is easy to see that the parts list is much shorter, so there’s a very high degree of confidence in the plant being markedly cheaper than a conventional design.

96 Nuclear fission

• Designed for the energy markets of the 21st Century. • Safe – Passive systems improve safety • Simple – Passive safety simplifies design, operation and maintenace • Economic – AP1000 competitive with CCGT • Use proven components already in operation Figure 6.9 Impression of the Westinghouse AP1000 reactor.

50% Fewer 35% Fewer 80% Less pipe* pumps valves

45% Less seismic building volume

80% Less cable

Compared with a conventional 1000 MW PWR Figure 6.10

Components in the AP1000 compared with a conventional design.

As well as benefits arising from the actual design philosophy of the reactor, there are improvements to be anticipated from the way construction is approached in modern nuclear reactor systems. Whichever design might be selected, an increasing proportion of the construction nowadays takes place remote from the reactor site itself, with sub-modules of the building being fabricated in factories and then shipped whole to the site for assembly. In this way, a large number of construction activities can be carried out in parallel and the on-site construction work is kept to a minimum. Quality control is also often easier in a factory setting than on the construction site.

Investor considerations—delivery and operational performance

97

Investor considerations—regulation So with all the benefits nuclear can offer to policy makers, and with a range of suitable technologies available, why is nuclear energy shunned in the UK as we speak? A variation on this question is often used by ministers and their teams to head off the nuclear debate. The line is basically: if nobody from the private sector is beating a path to my door wanting to build a nuclear reactor, why do we need to think about whether or not it’s a ‘good thing’? The fact is that something of a ‘Catch 22’ situation has been created. Although a new nuclear plant would only take four or five years to build, there are the planning and approvals processes to go through in the same way as for any other form of energy. However, there is also a three-year hurdle to overcome that is unique to nuclear energy, namely the need to get the reactor design approved by the Nuclear Installations Inspectorate, the UK’s nuclear regulator. There has previously been a strong tendency for UK regulators to request changes to make a design ‘better’or ‘more familiar’with the result that it becomes a unique station, with a lot of UK add-ons. This approach has led to the UK fleet being enormously varied (for instance virtually all the Magnox stations were different, and each reactor design used a slightly different design of fuel from the other stations). Such an approach has led to a missed opportunity in terms of economies of scale during operation in contrast to, for instance, the French who have a series of near-identical fleets (they have over thirty 900 MW plants all similar to one another, and more than twenty 1300 MW units, all of very similar design). More importantly in the context of new build investment, the UK approach implies a design which is still being changed as the licensing progresses, which has clear potential to introduce delays. The way forward is to adopt proven international reactor systems and to build them according to standard designs. On that basis, and with a streamlined—but not shortcut—planning and regulatory regime (where, for instance, the Public Inquiry focuses just on local issues) a potential predictable timeline for delivery would be as shown in Fig. 6.11.

Investor considerations—delivery and operational performance Korea and Japan provide many examples of construction and commissioning performance on time and within budget. Fig. 6.12 shows Tepco’s biggest site, at Kashiwazaki-Kariwa on the sea of Japan. It houses seven large boiling water reactors, delivering 8.2 gigawatts of

98 Nuclear fission

Revised energy policy issued

Licensable design selected

Phase 0/Input for Phase 1

Phase 1

3 years

Regulators' endorsement of site and design Licenses issued/planning consent received. Investment decision made

2 years

Plant on stream

Phase 2

5 years Construction contract signed

Figure 6.11

Potential timeline for a new nuclear plant in the UK.

Figure 6.12

The Japanese nuclear reactor site at Kashiwazaki-Kariwa.

Phase 3

electricity, 80% of Tokyo’s power demand, day in, day out. It is a very successful example of the benefits of series build. Another success story is the upwards trend in capacity factors of nuclear plants, as a result of sensible approaches to operating and maintenance and to standardization of fleets. Levels have risen steadily and the best stations in the world routinely achieve well over 90% (see Fig. 6.13). Any utility investing in a new reactor now would be really disappointed if they didn’t get at least a 90% capacity factor out of their new unit.

Investor considerations—waste 99

100.0 Net capacity factors 90.0

80.0

70.0

60.0

19

8 19 0 8 19 1 8 19 2 8 19 3 8 19 4 8 19 5 8 19 6 8 19 7 8 19 8 8 19 9 9 19 0 9 19 1 9 19 2 9 19 3 9 19 4 9 19 5 9 19 6 9 19 7 9 19 8 9 20 9 0 20 0 0 20 1 02

50.0

US

World

Source: WAN O and Nuclear Energy Institute Figure 6.13

Improvements in nuclear capacity factor.

Investor considerations—waste It is important now to look at a very emotive issue for many people namely the thorny issue of nuclear waste. It is most important to see this issue in context. There is a significant nuclear waste inventory in the UK. Most of that legacy is associated with the way in which we went about development of nuclear energy back in the 1940s, 50s and 60s, and any decision we make about new nuclear stations will not change that fact. Nor will it change the fact that those wastes are being managed safely and effectively. Waste associated with new reactors would only add a modest amount to this inventory. If the UK were to build a new series of reactors that would replace its capacity and run for 60 years, Fig. 6.14 shows the additional waste that would be generated compared with that which already exists at sites such as Sellafield, Dounreay, and the operating power stations. So a new build decision—even on the scale of a whole replacement fleet—would add only around one tenth to the volumes of existing wastes. Furthermore, the new build wastes would not bring any new technical challenges to add to those already faced. In fact the reverse is true, modern stations are designed with waste management and decommissioning in mind, and so the wastes are much easier to deal with than some of the challenges presented by the older legacy materials.

100 Nuclear fission

High and intermediate level waste 23,000m3 (10%)

216,000 m3

Legacy

Low level waste

80,000 m3 (3%)

2,750,000 m3

From 60 years operation of 10 AP 1000 reactors

Figure 6.14 Waste arising from potential new build nuclear planets in comparison with the existing UK nuclear waste legacy. Wastes from new stations would make only a small addition to existing stocks.

As for the reasons behind the dramatic differences in waste volumes between future and past systems, much has to do with the history of the older Magnox stations. These reactors were the workhorses—the very good workhorses—of the UK fleet for many years, and simply had a lot more waste associated with their operation than modern systems. They were relatively large and complex systems considering the amount of power produced, and fuel requirements were notably higher in terms of tonnes of fuel needed each year, as the burn-up levels achieved were far lower than later designs. Another factor is the fact that the industry carried out a lot of development work on sites like Sellafield in the 1940s, 50s, and 60s in order, for instance, to build the unique radiochemical processing facilities which are based there. That deals with the amounts of waste, but the concern to investors is not simply the quantities of material, but the process for dealing with it. The UK currently has no formal policy on management of the higher level wastes, so investors in a potential new plant simply don’t know what they will be required to do with their wastes at some point in the future. Until a clear policy is put in place (and only governments can do this) then this policy vacuum is essentially an open-ended liability for the investor. In terms of waste policy, what investors need to see is certainty. In the UK the Committee on Radioactive Waste Management (CoRWM) made recommendations in July 2006, which were accepted by the Government and welcomed by the industry. Progress should now begin towards selection of disposal sites. We already have a disposal route for low activity waste. Other countries have successfully addressed the issue of higher level wastes—Finland,

Public attitudes

101

Sweden, and the USA have all identified the way to proceed, with Switzerland and Japan moving that way. The issues are not technical, but political, in terms of agreeing the process and deciding where the final disposal site is to be.

Investor considerations—the electricity market In terms of an investor view of the electricity market and revenue issues, the long timescales are certainly an issue. As noted earlier, it would be five years from the announcement of a more positive policy until the likely date of a final investment decision. A further five years from that investment decision to the first date of power generation, and then an operating lifetime of perhaps 60 years. That represents a remarkably long time over which to project likely revenues and over which to judge the likelihood of any policy changes. Given the recent level of major change and intervention in the electricity market, it is perhaps not surprising that potential investors in nuclear are not rushing to place their money in nuclear projects. An investor looking at an outlay of perhaps £2 billion would have to take a very deep breath before making that sort of commitment in the absence of any reassurance from government that the goal posts are not going to move in some unpredictable and unhelpful way. Fuel and power prices are showing increasing volatility of late, and that works in favour of the nuclear industry, because of the price stability discussed earlier. But the energy sector in general—and nuclear issues in particular—are highly political. Governments can take a politically-motivated decision to phase out or to stop at any moment in time, and that knowledge also affects investor confidence. Public recognition by the government of the role that nuclear could play in delivering energy policy benefits (in particular with regard to climate change) would go some way towards reassuring investors that policy will not be changed ‘on a whim’.

Public attitudes Moving now from investor perspectives to look at public attitudes, we find that, with respect to nuclear, these can be very ambivalent. Fig. 6.15 illustrates one important question that was asked early in 2005. The response was that 35% of people were supportive, 30% opposed, but many people did not have a strong view. That is a major consideration because the ‘don’t knows’ are very easily swayed by an incident of the day, or the feeling of the day. However, the fact that more people were prepared to express a supportive opinion than a negative one on the issue is and contradicts what certain news media will suggest is the general flavour of public attitudes towards nuclear energy.

102 Nuclear fission

60%

Support

Oppose

50% 40%

35% 30%

30% 20% 10% 0% July 01 Figure 6.15

Dec 02

Dec 03

Dec 04

Recent UK public opinion survey concerning attitudes towards nuclear.

Those figures reflect the views of the general public as a whole. But if there were to be new stations built in the UK, they would almost certainly be built on existing sites where nuclear power stations are already operating, or are being decommissioned. When we survey the opinion around those existing sites, then we find a much more favourable response to whether or not these stations should be built. That again is encouraging, as people in these communities recognize that there is a station near them, and very often take the trouble to look below the surface and find out the reality for themselves about the issues surrounding nuclear generation in much more detail.

The longer term future The reactor technology options currently available have been outlined above, along with the argument in favour of building these to replace some of our existing power generation fleet. But looking at the bigger picture and thinking in the longer term, it becomes clear that more than just that is needed to make major cuts in the level of our carbon emissions. The Energy White Paper committed the UK government to achieving a 60% cut in emissions (relative to 1990 levels) by the year 2050. This was a level recommended by the Royal Commission on Environmental Pollution, in order to keep the threat of climate change in check. Yet a look at the UK’s overall energy usage as a nation in Fig. 6.16 soon illustrates the scale of that task. This chart of UK energy consumption in million tonnes of oil equivalent, shows that only a fraction of total energy use is consumed in the form of electricity. Even if we had no carbon emissions at all from the electricity sector, it would not even be close to a 60% cut in overall emissions when the coal, oil, and gas used elsewhere were considered.

The longer term future 103

Energy consumption (Mtoe) 100%

55.2

46.8

36.2

21.8

Total = 160 Mtoe Other

80% Solid fuel 60%

Oil

40%

Electricity Gas

20% 0 Transportation

Figure 6.16

Domestic (Heat, power & light)

Industry (HP&L)

Services (HP&L)

Breakdown of total UK energy demand.

One major initiative looking long term is an international programme called Generation IV. It is designed to reflect a ‘middle of the twenty-first century’ vision of energy needs, and to provide a pathway to systems that could start to operate between 2020 and 2040 and beyond. These are designed with sustainability, safety, reliability, and economic goals in mind, so they will offer a number of attractive features. They will maximize the energy we get out of the resources we put in. They will obviously be carbon-free, helping to combat climate change, whilst also minimizing future wastes. They will help to prevent proliferation, and ensure maximum physical protection, safety, and reliability. They are designed to give very low likelihood of unplanned events, and to eliminate the need for off-site emergency responses, so offer very high degrees of safety. In terms of economics, they give lifecycle cost advantages over other sources, and are generally small and modular rather than ‘big and beautiful’, because smaller systems often have advantages in deregulated markets. One key concept to highlight as an example, is the high temperature gas cooled reactor (HTR), and more specifically the pebble-bed design. There is an HTR operating now in Beijing, delivering 10 megawatts to their grid, and in South Africa there is an international consortium that will build a commercial pebblebed unit of 180 megawatts at Koeberg. The aim is to have that plant coming online around 2011, as a precursor to the longer-term journey. As mentioned above, these plants are modular, inherently safe, and they are highly suited to cost effective hydrogen production because of the high temperatures at which they operate. The outlet temperature in this design is about 950◦ C. Some future systems are looking at higher temperatures still.

104 Nuclear fission

Such temperatures offer the opportunity to do things differently, for instance opening up more direct—and therefore more efficient—routes to hydrogen production. Hydrogen is often talked about as an energy vector that can help the energy pattern in the world, but it has to be produced from carbon-neutral sources. Light water reactors, like any other form of power generation, can generate electricity which is used to produce hydrogen by electrolysis of water. Similarly, carbon-free power for such a process could also come from wind and other renewables. That is well proven, but is not the most economic or effective way to make hydrogen. But once we have nuclear plants which use heat in the high temperature range, then we have the opportunity to couple electricity generation with the heat output from the unit, and to move to thermally assisted ‘cracking’ of water to produce the hydrogen. Still carbon-free, but now also much more efficient, and that becomes increasingly important when we consider just how much hydrogen production will need to take place in future decades to underpin that shift in our transport systems. This is just one example of how the nuclear industry of tomorrow can offer much more than merely power generation. So, to summarize, the UK has opportunities select from internationally available, standardized systems, that are being built or considered elsewhere. In doing so, the UK can expect the same economic benefits that have driven countries such as Finland to make the same choice. The expectation is for reliable operation over 60 years at 90% capacity factor, and maybe even more. Looking towards the time that fusion might be available, there will be further choice of these more advanced systems which will be being deployed worldwide. They are not UK-unique systems. But will come from international consortia and deliver power to the UK grid on a routine basis, in the same way as France already gets most of its electricity routinely from nuclear energy.

The author Dr Sue Ion is an independent consultant in the Energy Sector having spent 26 years with BNFL and 10 years as its Chief Technology Officer. She is the UK representative on the IAEA Standing Advisory Group on Nuclear Energy and the Euratom Science and Technology Committee. She is also a member of the UK Council for Science and Technology and the EPSRC Council. Between 2004 and 2006 she was President of the British Nuclear Energy Society. She has spoken widely on matters associated with the nuclear industry, is a Visiting Professor at Imperial College, and a Member of the Board of Governors of the University of Manchester.

7.

Fusion energy Chris Llewellyn Smith and David Ward Introduction Principles of fusion Fusion fuel Fusion power stations Carbon contribution and other considerations The current status of fusion research The next steps—ITER and IFMIF ITER (International Tokamak Experimental Reactor) IFMIF (International Fusion Materials Irradiation Facility) Power plant studies Fast track studies and investor opportunities Conclusions Acknowledgement Resources and further information

105 106 107 107 108 109 113 113 115 116 117 118 119 119

Introduction Fusion powers the Sun and stars, and is potentially an environmentally responsible and intrinsically safe source of essentially limitless energy on earth. Experiments at the Joint European Torus (JET) in the UK, which has produced 16 MW of fusion power, and at other facilities, have shown that fusion can be mastered on earth. Fusion power is still being developed, and will not be available as soon as we would like. We are confident that it will be possible to build viable fusion power stations, and it looks as if the cost of fusion power will be reasonable. But time is needed to further develop the technology in order to ensure that it would be reliable and economical, and to test in power station conditions the materials that would be used in its construction. Assuming no major surprises, an orderly fusion development programme— properly organized and funded—could lead to a prototype fusion power station

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putting electricity into the grid within 30 years, with commercial fusion power following some ten or more years later. A fusion power station is effectively a tiny ‘artificial sun’.

Principles of fusion Reactions between light atomic nuclei in which a heavier nucleus is formed with the release of energy are called fusion reactions. The reaction of primary interest as a source of power on Earth involves two isotopes of hydrogen (Deuterium and Tritium) fusing to form helium and a neutron: D + T → 4 He + n + energy (17.6 million electric volts [MeV])

(7.1)

Energy is liberated because Helium-4 is very tightly bound: it takes the form of kinetic energy, shared 14.1 MeV/3.5 MeV between the neutron and the Helium-4 nucleus (a chemical reaction typically releases ∼1 eV [electron volt], which is the energy imparted to an electron when accelerated through 1 volt). To initiate the fusion reaction (1), a gas of deuterium and tritium must be heated to over 100 million◦ C (henceforth: M◦ C)—ten times hotter than the core of the Sun. At a few thousand degrees, inter-atomic collisions knock the electrons out of the atoms to form a mixture of separated nuclei and electrons known as a plasma. Being positively charged, the rapidly moving deuterons and tritons suffer a mutual electric repulsion when they approach one another. However, as the temperature—and hence their velocities—rises, they come closer together before being pushed apart. When the temperature exceeds 100 M◦ C, the more energetic deuterons and tritons approach within the range of each other’s nuclear force and fusion can occur copiously. There are two challenges. The first is to heat a large volume of deuterium plus tritium (D and T) gas to over 100 M◦ C, while preventing the very hot gas from being cooled (and polluted) by touching the walls: as described below, this has been achieved using a ‘magnetic bottle’ known as a tokamak. The helium nuclei that are produced by fusion (being electrically charged) remain in the ‘bottle’, where their energy serves to keep the gas hot. The neutrons, however, are electrically neutral and escape into, and heat up, the walls: this heat is then used to drive turbines and generate electricity. The huge flux of very energetic neutrons and heat (in the form of electromagnetic radiation and plasma particles) can damage the container. This leads to the main outstanding challenge, which is to make a container with walls sufficiently robust to stand up, day-in day-out for several years, to this neutron bombardment and heat flux.

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Fusion fuel The tiny amount of fuel that is needed is one of the attractions of fusion. The release of energy from a fusion reaction is ten million times greater than from a typical chemical reaction, such as occurs in burning a fossil fuel. Correspondingly, whereas a 1 GW coal power station burns 10,000 tonnes per day of coal, a 1 GW fusion power station would burn only about 1 kg of D+T per day. Deuterium is stable, and in one in every 3,350 molecules of ordinary water one of the hydrogen atoms is replaced by a deuterium atom. Deuterium can be easily, and cheaply, extracted from water. Tritium, which is unstable and decays with a half-life ∼12 years, occurs only in tiny quantities naturally. But, as described below, it can be generated in-situ in a fusion reactor by using neutrons from the fusion reaction impacting on lithium to produce tritium in the reaction: Neutron + Lithium → Helium + Tritium.

(7.2)

The raw fuels of a fusion reactor would therefore be lithium and water. Lithium is a common metal, which is in daily use in mobile phone and laptop batteries. Used to fuel a fusion power station, the lithium in one laptop battery, complemented by deuterium extracted from 45 litres of water, would (allowing for inefficiencies) produce 200,000 kW-hours of electricity—the same as 70 tonnes of coal: this is equal to the UK’s current per capita electricity production for 30 years. Fusion power stations Fig. 7.1 shows the conceptual layout (not to scale) of a fusion power station. At the centre is a D–T plasma with a volume ∼1000 m3 (actually contained in a ‘toroidal’ [doughnut shaped] chamber—see below). D and T are fed into the core and heated to over 100 M◦ C, a temperature routinely achieved at JET, as described below. The neutrons produced by the fusion reaction (1) escape the magnetic bottle and penetrate the surrounding structure, known as the blanket, which will be about 1 metre thick. In the blanket, the neutrons encounter lithium and produce tritium through reaction (2). There are various competing reaction channels, which do not produce tritium directly, but some of them produce additional neutrons that can then produce tritium (the production of additional neutrons can be enhanced, for example, by adding beryllium or lead). The upshot is that, on paper at least, it is possible to design fusion reactors that would produce enough tritium for their own use plus a small surplus to start up new plants: this will be tested at ITER (the International Tokamak Experimental Reactor), as described below. The neutrons will also heat up the blanket, to around 400◦ C in so-called ‘nearterm’ power plant models that would use relatively ordinary materials, and up to

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Lithium compund

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Fuel processing

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Figure 7.1 A conceptual fusion power station is similar to an existing thermal power station but with a different furnace and fuel. The figure is not to scale; in reality the fusion core would be a very much smaller part of the whole power station, and the ‘blanket’ would be ∼1 m thick while the plasma (which, as explained later in the text, would be contained in a toroidal chamber) would occupy ∼1000 m3 .

perhaps 1100◦ C in models that use advanced materials such as silicon carbide. The heat will be extracted through a primary cooling circuit, which could contain water or helium, that in turn will heat water in a secondary circuit that will drive turbines.

Attributes of fusion The advantages of fusion are: •

no CO2 or air pollution;

•

essentially unlimited fuel;

•

intrinsic safety;

•

‘internal’ costs (i.e. costs of generation) look reasonable—see the discussion of power plant studies below (‘external’ cost—impact on health, climate, and the environment—will be essentially zero);

•

it will meet a vital need.

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There is enough deuterium for millions of years, and easily mined lithium for several thousand years (after which it could be extracted from water). A key safety feature is that, although it will occupy a large volume, the amount of tritium and deuterium in a fusion reactor will be tiny: the weight of the hot fuel in the core will be about the same as ten postage stamps. Because the gas will be so dilute, there will be no possibility whatsoever of a dangerous runaway reaction. Furthermore, there is not enough energy inside the plant to drive a major accident and not much fuel available to be released to the environment if an accident did occur. What are the hazards? First, although the products of fusion (helium and neutrons) are not radioactive, the blanket will become activated when struck by the neutrons. However, the radioactivity decays away with half-lives of order ten years, and all the components could be recycled within 100 years. Should the cooling circuit fail completely, radioactivity in the walls would continue to generate heat, but the temperature would peak well below the temperature at which the structure could melt. Second, tritium is radioactive, but again the half-life is relatively short (12 years) and the possible hazard is not very great. In any case it will be easy to design reactors so that even in the worst imaginable accidents or incidents (such as earthquakes or aircraft crashes) only a small percentage of the tritium inventory could be released and evacuation of the neighbouring population would not be necessary.

The current status of fusion research The most promising magnetic configuration for confining (‘bottling’) fusion plasmas is called a tokamak (a contraction of a Russian phrase meaning toroidal chamber with a magnetic coil). The basic layout of a tokamak is shown in Fig. 7.2. An understanding of how tokamaks work is not needed to follow the rest of this paper, but for readers with a technical background who are interested: • Asmall amount of gas (hydrogen or deuterium in most experiments; deuterium

and tritium in some experiments at JET and in an actual fusion reactor) is injected into the toroidal (doughnut shaped) vacuum chamber after the magnetic field coils have been switched on. • A current is driven in a coil wound around the column at the centre, which

acts as the primary of a transformer. This drives an electric current (∼5 MA in JET) through the gas, which acts as the secondary. •

The electric current heats the gas, and turns it into a plasma. It also produces a magnetic field which, combined with the magnetic field produced by the

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Magentic Circuit (iron transformer core) Inner Poloidal Field Coils (primary transformer circuit)

Toroidal Field Coils

Outer Poloidal Field Coils (for plasma positioning and shaping) Poloidal field Toroidal field Ip

JG0

6.41

0-2c

Plasma with Plasma Current Ip (secondary transformer circuit) Resultant Helical Magnetic Field (exaggerated)

Figure 7.2 In a tokamak, the fusion fuel is held in a toroidal chamber surrounded by magnets. A current is induced in the fuel by transformer action and, together with the magnets, produces a helical magnetic structure that holds the hot fuel away from the wall.

external coils, serves to ‘confine’ the plasma, i.e. hold it away from the walls and provide very good thermal insulation. •

The current induced by transformer action can only heat the plasma to about one third of the temperature needed for copious fusion to occur. Additional heating power must therefore be supplied, by mechanisms that serve also to drive the current (which is essential for plasma confinement) thereby keeping it flowing.

•

This additional heating and ‘current drive’ can be provided by injecting either microwaves (rather as in a microwave oven) or beams of very fast, energetic neutral particles, produced by banks of small accelerators, which transfer energy to the plasma through collisions, or both. Many MWs of heating power can be supplied by these means.

In addition to heating and current drive systems, tokamaks are equipped with ‘diagnostic’devices that measure the magnetic field, electron and ion temperatures and densities, the plasma pressure position and shape, neutron and photon production, impurities etc., and monitor the development of instabilities Three parameters control the fusion reaction rate: 1. The plasma temperature (T), which as already stated must be above 100 M◦ C.

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111

2. The plasma pressure (P). The reaction rate is approximately proportional to P2 . 3. The ‘energy confinement time’ (τE ) defined by: τE =

energy in the plasma power supplied to heat the plasma

τE measures how well the magnetic field insulates the plasma. It is obvious that the larger τE , the more effective a fusion reactor will be as a net source of power. It turns out that the ‘fusion product’ P (in atmospheres) × τE (in seconds) determines the energy gain of the fusion device, and this must be ten or more in a fusion power station. The ‘fusion performance plot’ (Fig. 7.3) of PτE vs. T, which shows data points from different tokamaks, indicates the substantial progress towards power station conditions that has been achieved in recent decades. Semi-empirical scaling laws have been devised that interpolate rather accurately between results from machines with very different sizes, magnetic fields and plasma currents. The scaling law for confinement time is shown in

Fusion product PiτE (atmosphere secs)

10

D-T Tokamaks JET 1997 TFTR 1994/5

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Power plant conditions

High energy gain ITER Breakeven JT-60U

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10 100 Central ion temperature Ti (million°C)

1000

Figure 7.3 Selected results from different tokamaks demonstrate substantial progress over recent decades from the low temperature, low energy gain points at the bottom left. Temperatures above 100 M◦ C are now routinely achieved and an energy gain of around one has been reached. A power plant needs an energy gain above ten and this should be achieved in ITER.

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ITER

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JET 0.1

0.01 World Wide Data Base (13 Devices) 0.001 0.001

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JG06.410-4c

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10

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Figure 7.4 Confinement times (in seconds) measured at a range of very different tokamaks are well described by a semi-empirical scaling law that ‘predicts’ the confinement time as a function of the tokamak’s size, magnetic field and plasma current (and other parameters). The prediction for ITER is shown.

Fig. 7.4. This figure makes us rather confident that the power station sized device called ITER, which (see below) will be constructed in the near future, will perform as advertised. ITER should confirm that it is possible to build a fusion power station (provided that, meanwhile, work on the materials that will be used to construct a power station proceeds apace, as described below). JET is the closest existing tokamak to ITER in size and in performance (in many, if not all, parameters). It is also the only tokamak in the world that can be operated with tritium, although most of the time Deuterium alone (which has essentially the same plasma properties as a D—T mixture, but a much lower fusion cross-section) is used—as in other tokamaks—in order to keep activation to a minimum. JET holds the world record for fusion energy and power production in the two pulses shown in Fig. 7.5, which also shows the record pulse from the now closed Tokamak Fusion Test Reactor (TFTR) at Princeton, which is the only other tokamak to have been capable of using tritium. The record energy pulse produced was ∼4 MW for five seconds, after which the pulse was ended in order to keep within the neutron production budget. Record power, of 16 MW, was produced when trying to push up the plasma pressure—but this could only be

The next steps—ITER and IFMIF 113

JET (1997)

15

Q~0.65

Fusion power (MW)

TFTR (1994) 10

JET (1997)

5

Q~0.2 JG06.410-5c

JET (1991) 0 0

1.0

2.0

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4.0

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Figure 7.5 Fusion power produced in record pulses in D-T plasmas at JET and TFTR. Here Q is the fusion power generated/heating power, which is expected to be at least 10 at ITER.

sustained for a short time. The predicted performance of ITER is based on the lower power, steady plasmas, although as discussed below, one of the major goals of ongoing tokamak research is to find ways of pushing up the pressure (and hence the fusion reaction rate, which P2 ) to higher values in a controlled way.

The next steps—ITER and IFMIF Two intermediate facilities are necessary (which, see below, can and should be built in parallel) before the construction of a prototype fusion power station, fully equipped with turbines etc., will supply power to the grid. These are: ITER (International Tokamak Experimental Reactor) ITER, which is shown in Fig. 7.6, will be approximately twice the size of JET in linear dimensions, and operate with a higher magnetic field and current flowing through the plasma. The aim of ITER is to demonstrate integrated physics and engineering on the scale of a power station. The design goal is to produce 500 MW of fusion power, with an input ∼50 MW. JET can only operate for up to one minute because the toroidal coils that produce the major component of the magnetic field are made of copper and heat up. This would not be acceptable in a fusion power station, and ITER will be equipped with

114 Fusion energy

Figure 7.6 The ITER project, ready for construction, is designed to produce at least 500 MW of fusion power. It is similar in configuration to JET but twice as large (in each dimension).

super-conducting coils, that will allow indefinite operation if the plasma current can be kept flowing (the design goal is above ten minutes). Super-conducting tokamaks already exist, and others are under construction, but super-conducting coils have not so far been used in really large tokamaks capable of using tritium. ITER will also contain test blanket modules that, for the first time, will test features that will be necessary in power stations, such as, for example, the in situ generation and recovery of tritium. A major goal of ITER is to show that existing plasma performance can be reproduced with much higher fusion power than can be produced in existing devices. Developments with the potential to improve the economic competitiveness of fusion power will also be sought (in experiments at existing machines as well as ITER). The main goals are: 1.

Demonstrating that large amounts of fusion power (10 times the input power) can be produced in a controlled way, without provoking uncontrolled instabilities, over-heating the surrounding materials or compromising the

The next steps—ITER and IFMIF 115

purity of the fusion fuel. These issues are successfully managed in existing devices but will become much harder at higher power levels produced for longer times. ITER is designed to tolerate this but it remains a big challenge. 2.

Finding ways of pushing the plasma pressure to higher values (the rate at which fusion occurs and produces power, is proportional to the square of the pressure) without provoking uncontrollable instabilities. This would allow a power plant to operate either at higher power density or with reduced strength magnets, in either case lowering the expected cost of fusion generated electricity.

3.

Demonstrating that continuous (‘steady state’) operation, which is economically and technically highly desirable if not essential, can be achieved without expending too much power. There is optimism that the plasma current can be kept flowing indefinitely by ‘current drive’, from radiofrequency waves and particle beams, boosted by a self generated (‘bootstrap’) current, however this must be optimized to minimize the cost in terms of the power needed.

Prototypes of all key ITER components have been fabricated by industry and tested. ITER, which will cost D4.5 billion, will be funded and built by a consortium of the European Union, Japan, Russia, USA, China, South Korea, and possibly India. Construction will begin, at Cadarache in France, once planning permission—which is being sought at the time of writing—is granted. IFMIF (International Fusion Materials Irradiation Facility) Those ‘structural’ materials, from which fusion power stations will be built, that are close to the plasma will be subjected to many years of continuous bombardment by a ∼2.5 MWm−2 flux of 14 MeV neutrons. This neutron bombardment will on average displace each atom in nearby parts of the blanket and supporting structures from its equilibrium position some 30 times a year. Displaced atoms normally return to their original configuration, but occasionally they do not and this weakens the material. On the basis of experience of neutroninduced damage in fast breeder reactors, it seems that materials can be found that would meet the target of a useful lifetime of around five years before the materials would have to be replaced. The much higher energy fusion neutrons will, however, initiate nuclear reactions that can produce helium inside the structural materials, and there is a concern that the helium could accumulate and further weaken them. The so-called plasma-facing materials and a component called the divertor (through which impurities and the helium ‘ash’ produced in D-T fusion are exhausted) will be subjected to additional fluxes of 500 kWm−2 and

116 Fusion energy

10 MWm−2 respectively in the form of plasma particles and electromagnetic radiation. Special solutions are required and have been proposed for these areas, but they need further development and testing in reactor conditions. Various materials are known that may be able to remain robust under such bombardments (it is in any case foreseen that the most strongly affected components will be replaced periodically). However, before a fusion reactor can be licensed and built, it will be necessary to test the materials for many years in power station conditions. The only way to produce neutrons at the same rate and with essentially the same distributions of energies and intensity as those that will be experienced in a fusion power station, is by constructing an acceleratorbased test facility known as IFMIF (International Fusion Materials Irradiation Facility). Further modelling and proxy experiments (for example, using fission and neutrons produced by spallation sources) can help identification of suitable candidate materials. But they cannot substitute for IFMIF, and neither will testing in ITER be sufficient, because (i) the neutron flux will only be ∼30% that in an actual fusion power station, in which the fusion power will be several GWs, and (ii) as an experimental device, ITER will only operate for at most a few hours a day, while IFMIF will operate round the clock day-in day-out. IFMIF, which will cost ∼ D 800 M, will consist of two 5 MW accelerators that will accelerate deuterons to 40 MeV (very non-trivial devices). The two beams will hit a liquid lithium target that will produce neutrons, stripped out of the deuterons, with a spread of energies and an intensity close to that generated in a fusion reactor. These neutrons will provide estimated displacement rates (in steel) of 50, 20, and 1 displacements per atom per year over volumes of, respectively, 0.1, 0.5, and 6 litres. Power plant studies A power plant conceptual study has recently been completed under the auspices of the European Fusion Development Agreement. This study provided important results on the viability of fusion power, and inputs to the critical path analysis of fusion development described below. Four models (A–D) were studied as examples of a spectrum of possibilities. Systems codes were used to vary the designs, subject to assigned plasma physics and technology rules and limitations, in order to produce an economic optimum. The resulting parameterization of the cost of fusion generated electricity as a function of the design parameters, should be used in future to prioritize research and development objectives. The near-term models (A and B) are based on modest extrapolations of the relatively conservative design plasma performance of ITER. Models C and D assume progressive improvements in performance, especially in plasma shaping, stability, and protection of the ‘divertor’, through which helium ‘ash’ and

Fast track studies 117

impurities will be exhausted. Likewise, while Model A is based on a conservative choice of materials, Models B–D would use increasingly advanced materials and operate at increasingly higher temperatures (which would improve the ‘thermodynamic efficiency’ with which they turn fusion power into electricity). The power plant study shows that the cost of fusion generated electricity decreases with the electrical power output (Pe ) approximately as P−0.4 . It was e assumed that the maximum output acceptable to the grid would be 1.5 GW. Given the increase of temperature and hence thermodynamic efficiency, the size and gross fusion power needed to produce Pe = 1.5 GW decreases from model A (with fusion power 5.0 GW) to D (fusion power 2.5 GW). The cost of electricity, which is dominated by the capital cost, also decreases with size from 9 Eurocents/kWhr for an early model A to 5 Eurocents/kWhr for an early model D (these costs would decrease as the technology matures). Even the first cost would be competitive with other generating costs if there was a significant carbon tax, which now effectively exists in Europe with the Emissions Trading Scheme. If acceptable and necessary, larger plants (with Pe > 1.5 GW) would be more cost effective. The power plant study shows that economically acceptable fusion power stations, with major safety and environmental advantages, seem to be accessible through ITER with material testing, if possible in parallel, at IFMIF (but without major material advances). The above discussion assumes that the first prototype fusion power station will be based on a conventional (ITER/JET-like) tokamak. This will almost certainly be the case, unless ITER produces major surprises. Alternative magnetic confinement configurations (‘spherical tokamaks’; ‘stellerators’) are, however, under development that have certain theoretical advantages, and could form the basis for later prototypes and actual fusion power stations. Meanwhile they provide additional insights into the behaviour of plasmas and fusion technology which feed into the mainstream, conventional tokamak, line.

Fast track studies A detailed study of the time that will be needed to develop fusion has recently been completed at UKAEACulham. It was assumed that construction of ITER and IFMIF both begin in the immediate future. The information that will be needed to finalize the design of the first prototype fusion power station, which has become known as DEMO (for Demonstrator), was identified and estimates were made of when this information will be provided by ITER and IFMIF. Assuming just in time provision of the necessary information, this led to the construction timetable for DEMO shown in Fig. 7.7. Commercial fusion power stations would follow some ten or more years after DEMO comes into operation.

118 Fusion energy

2005 ITER

IFMIF

DEMO

2015

2025

design

operate

construct

explore concept

2035

operate

construct

R&D

design

construct

power production JG06.410-6c

Figure 7.7 Possible time-line for the construction of the devices (ITER and IFMIF) that are needed before a prototype power station (DEMO) can be built, and for construction of DEMO itself. This is a very much simplified summary of the results of a detailed study.

The Culham fast track timetable reflects an orderly, relatively low risk, approach. It could be speeded up if greater financial risks were taken, for example, by starting DEMO construction before in situ tritium generation and recovery have been demonstrated. The risks could be reduced—and the timetable perhaps speeded up—by the parallel construction of multiple machines at each stage. Fig. 7.7 assumes that ITER and IFMIF are approved at the same time, which is highly desirable but may not be realistic (some delay in IFMIF construction might however be tolerable without comprising the end date). It should be stressed generally that the fast track model is a technically feasible plan, not a prediction. Meeting the timetable will require a change of focus in the fusion community to a project orientated ‘industrial’, approach, accompanied of course by the necessary funding and political backing.

Conclusions The world faces an enormous energy challenge, as a result of rising energy use, and the fact that burning fossil fuels (which currently provide 80% of primary energy) is driving potentially catastrophic climate change and, when not managed carefully, producing debilitating pollution. The response must be a cocktail of measures: we must strive to use energy more efficiently, and renewables should play a role where appropriate. But there are in principle only four ways of meeting a large fraction of world energy demand: continuing use of fossil fuels (as long as they last); solar power (but realizing its potential requires major breakthroughs); nuclear fission; and fusion. With so few horses in the race, we cannot afford not to back fusion. Given the remarkable progress that has been achieved in recent decades, we are confident that fusion will be used as a commercial power source in the long term. We are less confident that fusion will be available commercially on the time scale outlined above, which would require adequate funding of

The authors 119

a properly focused and managed programme, and that there are no major surprises. However, given the magnitude of the energy challenge and the relatively small investment that is needed on the ($3 trillion pa) scale of the energy market, we are absolutely convinced that accelerated development of fusion would be fully justified.

Acknowledgement This work was funded by the UK Engineering and Physical Sciences Research Council and Euratom.

Resources and further information General information on fusion can be found in the recent book, Fusion, the Energy of the Universe, G. McCracken and P. Stott, Elsevier (2005), ISBN 0-12-481851X, and in La Fusion Nucléaire, J. Weisse, Presse Universitairs de France (2003), ISBN 2-13-053309-4 or on the UKAEA Culham web site www.fusion.org.uk The EU studies of fusion power plant concepts are available at http://www.wfda. org/portal/downloads/efda_rep.htm: for a summary see A Conceptual Study of Commercial Fusion Power Plants, D. Maisonnier et al., EFDA-RP-RE5.0 (2004). The analysis of the development path for fusion is given in Accelerated Development of Fusion Power by I. Cook et al., February 2005, UKAEA FUS 521, available at http://www.fusion.org.uk/techdocs/ukaea-fus521.pdf

The authors Prof Sir Chris Llewellyn Smith FRS is Director of UKAEA Culham Division, which operates JET on behalf of Euratom and houses the UK’s fusion research programme. He spent the first part of his career as a theoretical high energy physicist, before becoming Chairman of Oxford Physics, Director General of CERN (1994–98), and President and Provost of University College London. His scientific contributions and leadership have been recognized by awards and honours in seven countries in three continents. He has also spoken widely and written on science policy and energy issues. Dr David Ward is a fusion scientist at UKAEA Culham. Having first worked on theory and experiments at JET, he now plays a leading role in pan-European fusion power station design studies and studies of the socio-economics of fusion.

8.

Photovoltaic and photoelectrochemical conversion of solar energy Michael Grätzel Introduction Principles Conversion efficiencies Cost and supplies of raw materials How PV cells are developing Second generation thin film PV cells Mesoscopic solar cells The benefits of the mesostructure Opportunities for performance improvement Third generation photovoltaic cells Field tests of DSC modules Industrial DSC development Summary Acknowledgements Resources and further information

120 120 122 124 125 125 126 127 129 131 131 133 133 134 134

Introduction The Sun provides about 100,000 Terawatts (TW) to the Earth, which is approximately ten thousand times greater than the world’s present rate of energy consumption (14 TW). Photovoltaic (PV) cells are being used increasingly to tap into this huge resource and will play a key role in future sustainable energy systems. Indeed, our present needs could be met by covering 0.5% of the Earth’s surface with PV installations that achieve a conversion efficiency of 10%.

Principles Fig. 8.1 shows a simple diagram of how a conventional photovoltaic device works. The top and bottom layers are made of an n-doped and p-doped silicon,

Principles

e−

Photons

A

121

+

Load B

−

Figure 8.1 Schematic diagram of how a conventional solid state photovoltaic device works.

where the charge of the mobile carriers is negative (electrons) or positive (holes), respectively. The p-doped silicon is made by ‘doping’ traces of an electron-poor element such as gallium into pure silicon, whereas n-doped silicon is made by doping with an electron-rich element such as phosphorus. When the two materials contact each other spontaneous electron and hole transfer across the junction produces an excess positive charge on the side of the n-doped silicon (A) and an excess negative charge on the opposite p-doped (B) side. The resulting electric field plays a vital role in the photovoltaic energy conversion process. Absorption of sunlight generates electron-hole pairs by promoting electrons from the valence band to the conduction band of the silicon. Electrons are minority carriers in the p-type silicon while holes are minority carriers in the n-type material. Their lifetime is very short as they recombine within microseconds with the oppositely charged majority carriers. The electric field helps to collect the photo-induced carriers because it attracts the minority carriers across the junction as indicated by the arrows in Fig. 8.1, generating a net photocurrent. As there is no photocurrent flowing in the absence of a field, the maximum photo-voltage that can be attained by the device equals the potential difference that is set up in the dark at the p-n junction. For silicon this is about 0.7 V. So far, solid-state junction devices based on crystalline or amorphous silicon (Si) have dominated photovoltaic solar energy converters, with 94% of the market share. These systems have benefited from the experience and material availability generated by the semiconductor industry and they are at a mature state of technical development in a rapidly growing market. Fig. 8.2 shows the photovoltaic peakpower installed annually from 1988 to 2003. In 2004 and 2005 the trend has continued, the peak-powers being 1.15 GW and 1.5 GW respectively. By 2010 the module output sales are expected to quadruple again, reaching 6 GW. This impressive growth is being fuelled by attractive feed-in tariffs.

122 Photovoltaic and photoelectrochemical conversion of solar energy 800 744.1

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World PV Cell/Module Production (in MW)

Figure 8.2 The increase in worldwide production of PV modules during the last 15 years. The market growth rate in the last decade has been over 30%.

Share prices in solar cell companies are soaring and revenues are predicted to increase from 8.3 billion US$ in 2004, to 36.1 billion US$ in 2010, with pretax profits rising from 1.2 to 6.4 billion US$ over the same period. By 2030 the yearly PV module output is expected to attain 300 GW (PV-TRAC, 2005). However, this is still too little to make a major impact because the world’s energy consumption will by then approach 20 TW; in addition photovoltaic power figures are expressed in peak-watts, that is the output reached only in full sunshine at 1 kW/m2 incident light intensity. The real power, averaged over day and night and the 4 seasons is about 3–10 times lower (depending on geographical location as well as direction and angle of orientation of the panels). Nevertheless, based on the recent growth rates, it has been predicted (Zweibel, 2005) that by 2065 all the world’s energy needs could in principle be met by photovoltaic cells.

Conversion efficiencies The conversion efficiency of a solar cell is defined as the ratio of its electric power output to the incoming light intensity that strikes the cell. The internationally accepted standard test condition (STC) uses as a reference sunlight (viewed at 48 degrees to overhead) normalized to 1 kW/m2 , with the temperature kept at 298 K. The conversion efficiency is determined by measuring the photocurrent

Conversion efficiencies 123

(that is, the electrical current induced by light) as a function of the cell voltage using the formula η = Jsc Voc FF/Is

(8.1)

Here Jsc is the short-circuit photocurrent density, Voc the open circuit voltage, Is the incident solar intensity (1000 W/m2 ) and FF the fill factor defined as the electric power produced at the maximum power point of the J-V curve divided by the product Jsc × Voc . Fig. 8.3 shows the history of confirmed ‘champion’ laboratory cell efficiencies. The performance of conventional solar cells is approaching a plateau; only incremental improvements have been accomplished in the last decade despite dedicated R&D effort. The efficiency of multi-junction cells based on III/IV semiconductors has progressed recently beyond 30%. However, the cost of these devices is very high, limiting their application to space and solar concentrators. In the latter case sunlight is concentrated typically several hundred times by a mirror or a lens before striking the photovoltaic device. This will reduce cost if the price per square metre of the solar concentrator is below that of the photovoltaic cell. However, solar concentrators need to track the sun and work well only in direct sunlight in the absence of haze, considerably limiting their potential for practical applications. The efficiencies reached with commercial solar cell modules are significantly lower than those of the best laboratory cells due to losses incurred

36

Multijunction concentrators

32

Crystalline Si Cells

Spectrolab Japan Energy

Single crystal Multicrystalline

28 Efficiency (%)

Spectrolab

Three-junction (2-terminal, monolithic) Two-junction (2-terminal, monolithic)

NREL/ Spectrolab

NREL NREL

Thin Film Technologies Cu(In,Ga)Se2 CdTe Amorphous Si:H (stabilized)

24

Emerging PV

20

Stanford

Spire ARCO Westing -

Kodak

Sharp

ARCO

Solarex

NREL

8

United Solar University of Lausanne

Boeing

4 RCA

0 1975

University RCA of Maine RCA RCA RCA RCA

1980

United Solar Photon Energy

Boeing RCA

NREL

NREL NREL

Boeing AMETEK

Kodak

NREL Cu(In,Ga)Se2 14 x concentration UNSW NREL

Euro-CIS

Boeing

Masushita Monosolar

UNSW

NREL

University So. Florida

No. Carolina State University

Boeing

Georgia Tech

Varian

Organic cells house (various technologies)

12

UNSW Georgia Tech

Dye cells

16

UNSW

UNSW

Spire UNSW

Solarex Groningen Siemens Princeton

University of Lausanne Cambridge UCSB

Kodak

1985

1990

1995

University University Linz Berkeley Linz

2000

2005

Figure 8.3 A history of best cell efficiencies. All plotted values have been confirmed and were measured under standard test conditions